You saying "You have no right to act like he needs to improve" and "No one has a right to tell anyone else what they're allowed to say" felt defensive to me,

Those statements are true.

His positive responses are perfectly good, and they come from who he is as a person. To say that he's not good enough and must improve because he finds the silver lining in things is wrong.

We also have a human right to autonomy and freedom of expression, and he can express himself however he wants to whenever he wants to. It's absolutely true that no one has a right to say "when I say x, you need to respond with y".

maybe someone has tried to control what you say in the past and now you want to defend him so I don't control what he says

Geez, you came here for help and you end up trying to diagnose MY issues. That's quite funny.

I'm sorry if I have offended you, I think we just view communication differently

I'm not offended, but you came asking for help, I did my best to advise you, and you've attacked me for being defensive, projecting my own issues, acted like I made accusations towards you, etc. If this is the way things go when you disagree then I would avoid engaging with you myself.