Both are technically correct, though awkward since you are repeating "You aren't/weren't like him." The whole concept of saying "I meant" followed by something you already said doesn't make sense; you say "I mean" to reiterate/state what you said in a different way, not the same way. I added some other comments as well: Dialogue 1. Person A. - He is lazy. You aren't like him. Person B. - What? Person A. - I meant you aren't like him. I would change this to: I mean you aren't like him. Though "meant" in this context is not wrong, it sounds better to use the present tense. I would also consider changing the phrase so that it isn't the same thing twice. Dialogue 2. Person A. - He was lazy. You weren't like him. This sounds awkward. It would be better to say "You aren't like him" in present tense. Using past tense implies that Person B is now like the lazy person. Person B. - What? Person A. - I meant you weren't like him. Again, I would change it to "I mean you aren't like him" in present tense. Hopefully this helps!

The second answer is not quite correct. In using the past tense, it changes the meaning and means it no longer makes sense. For the first one, it does make sense, but generally you would use "You're not like him" as opposed to "You aren't like him"

Yes, both dialogueS are OK, but because similarity to another person could be seen as an intrinsic, unchanging characteristic of someone, it's likely that the second dialogue would also have "you aren't like him", even if the laziness was in the past (and presumably transient).