Just because..., (it) doesn’t mean...

Remove the apostrophe from 'doesn't'.

“Just because I was mean to you, it does not mean you should be mean to me.” OR
“Just because I was mean to you, does not mean you should be mean to me.” OR
“Just because I was mean to you, that does not mean you should be mean to me.”

In the first, what subject is "it" referring to? It's like the "they" in "they say you should wait thirty minutes before swimming after a meal." Ambiguous and airy. In the third, "that" is similarly vague.

The second is preferable, and to me, reads better both with "doesn't" and "does not".

How about:
"Just because I was mean to you, you should not be mean to me."

Ing—I like your sentence but I think it might be preferable to switch the clauses: "You should not be mean to me just because I was mean to you." Otherwise it seems like "you should not be mean to me" is the direct result of my being mean to you. (In other words, your kindness is a response to my meanness, which doesn't make sense.)

Yes, Max, I agree your sentence sounds even better.

I guess some of the questions we have on this forum are examples of spoken language, which are probably alright anyway if that is how people speak in a particular setting or group and everybody gets the intended meaning.

The reason all those forms are acceptable is because, based on linguistic theory, that spot after the comma can be filled by a complement or a referent, the complement being "that" and the referent being "it". Both are transitional, but the "it" version is redundant in the information it effectively relates, that being some situation X where person B was mean to person A at some time where tpresent with the condition of meanness having being asserted)...if that makes any sense :P. Thusly, that is somewhat preferable in simply acting as a segue into the next action while holding onto the information previously stated.

Nevertheless, redundancy occurs throughout language in many facets (i.e. adverbs differing from adjectives only in what they modify and an -ly ending, the meaning of the adjective base is the same, the -ly simply shows acknowledgement that that adjective (modifier) is modifying a verb instead of a noun

All three version of the sentence are fine. The differences between them are mostly a matter of emphasis, but are so minute that you really shouldn't worry about them. And please use the contraction, it sounds very stilted otherwise.

I would drop the comma entirely and go with this: "Just because I was mean to you doesn’t mean you should be mean to me." This would be a bear of a sentence to diagram, though.

The "it" nicely summarises the first clause to act as a concise subject of "doesn't mean", otherwise if you leave it out (your second sentence) there is a long (seven word) clause to act as subject. "That" is not as good a choice as "it" in my view. Your first sentence ("it doesn't mean") is the best. To avoid it altogether, as suggested, by rearranging the whole thing, is an artifice, well, to avoid the problem! And "doesn't" is just fine, nothing wrong wrong with it. The whole thing is idiomatic and perfectly sound grammatical English.

I think all your three sentences are correct/in common usage except that the second has an unnecessary comma.

CAUTION: I'm not a native English speaker.

I've just come across this post. IMHO all versions are illogical if not incorrect. Whether the subject is missing in the main clause ("doesn't mean...") or it is a pronoun that is supposed to refer to the subordinate clause, the subordinate clause must respond to the question "what doesn't mean...?". However, a "just because..." clause responds to a question "why?".

Better variations could be
"The fact that I was mean to you doesn’t mean you should be mean to me."
("The fact that..." responds to a "what?" question.) or
"Just because I was mean to you you shouldn't necessarily be mean to me."
(The main clause is complete and the subordinate clause may have the function of a causal adjunct, responding to the question "why?".)

The fact that there is no uncomplicated solution stems from the fact that while both the subject and the object respond to a "what?" question, only a subordinate clause that substitutes the object can be introduced with "that", one that substitutes the subject cannot:
"I think that I was mean to you." (Correct, the subordinate clause represents the object of "I think".)
"That I was mean to you doesn't mean you should be mean to me."* (Incorrect, the subordinate clause represents the subject. I don't know any reason why it is wrong other than it sounds wrong. Note that in my native language, Hungarian, its equivalent is perfectly correct.)
Since this is incorrect, it needs to be worked around with the ill-sounding "the fact that" or the illogical "just because".

All three are fine except for the comma in the middle one, as the subject there is the whole clause "Just because I was mean to you". Otherwise, that construction is perfectly OK - "Just because it's raining doesn't mean we have to stay in all day."

@Jakab Gipsz - a "because" clause might answer "why", but "just because" is often used in a different, idiomatic, way, really meaning something like "The simple fact that" . Here are some titles of books found on Google Books:

"Just Because They'Ve Left Doesn't Mean They're Gone"
"Just Because It's Not Wrong Doesn't Make It Right"
"Just Because You Can Doesn't Mean You Should"

"Just because" is used quite a lot in idiomatic constructions with "doesn't mean". For example this quote is often attributed to Joseph Heller:
“Just because you're paranoid doesn't mean they aren't after you"

It would seem that the pronoun-less version is much more common; here are some actual Google counts:
"Just because I love you doesn't mean" - 148
"Just because I love you it doesn't mean" - 36
"Just because I love you that doesn't mean" - 15

I'd also suggest that there's a slight difference between the "it" and the "that" versions. There seems to me to be a stronger stress on "that", emphasising that the first action doesn't justify the second (in the speaker's view).

I'm afraid your example "Just because I was mean to you you shouldn't necessarily be mean to me." may satisfy your grammatical criteria, but sounds less natural to me than the original version, which is simply more idiomatic.

Your last point about "That I was mean to you doesn't mean you should be mean to me." This sentence is in fact correct, as "that" clauses are Noun clauses (or Nominal clauses) and fill the functions of nouns, subject, object etc, just as in your example. They are not used in Subject position so often (it is rather formal, or used for literary effect - it's a kind of fronting), but as a Direct Object, as in the sentence "I think that I was mean to you." - What do I think? - "that I was mean to you".

Here is an example from Anthony Trollope (The Duke's Children):
"That she should be told that she had disgraced herself was terrible to her."

Other nominal clauses include "wh-clauses" - both Nominal Relative clauses - "What I'd really like now is a nice big cup of coffee" (Subject) and interrogative clauses - "I wonder where they're taking us" (Direct Object)

Non-finite phrases with infinitives and gerunds also function as Noun clauses - "I like to dance" (Direct Object), - "Smoking cigarettes is bad for you" (Subject)

They can also fill some other Noun functions
"And that’s exactly what he did" (Subject complement)
"His dream, that one day he would play for PSG, was never out of his head" (Appositive)

There's an article about the "just because ... doesn't mean" construction for ESL/EFL teachers, with lots of examples at: http://www.stickyball.net/writing.html?id=383

Another site with more examples, of all three types: http://www.brainyquote.com/quotes/keywords/just_because.html

And there's another discussion about it here: http://english.stackexchange.com/questions/95964/grammar-just-because-a-doesnt-mean-b