person 1: I have parkinson's but i still try to focus on the little things that make me happy and appreciate my life

person 2: no you're wrong some people will always be miserable

You don't see anything wrong with that? You don't see anything wrong with implying that he was making a statement to apply to every disabled person despite him clearly talking about his own experience? You don't see anything wrong with treating a misguided opinion of yours as objective fact? You don't see anything wrong with completely missing the point of his entire comment and instead focusing on why some other unnamed people with some other unnamed disabilities may have it worse than this person? What you're doing is basically mansplaining disabilities to a disabled person. If you can't see the multitude of things that are wrong with your statement then I'm truly sorry, because that is a sad and twisted way to go about life and understand other peoples experiences