The sub's name is r/roastme . It's meant to be as intuitive as possible. If he posted that anywhere else, I would have said the same thing. You are meant to be mean and hurtful.

It's like debating and unpopular opinion. Ex. Using nuclear weapons. Judges in a contest will likely award people in favour prize if the point is well made even though they might be weak.

It's the challenge which makes this post gold. She is clearly beautiful and it's very hard to criticize someone like that with no background info and only a beautiful picture to critique.

In that sub there are amputees, disfigured people and survivors who ask to be roasted. It's done in jest not to be taken seriously. People will get hurt but it's the poster who asked for it. There are no lines which cannot be crossed.

Calling the commentator mentally ill is immature and you clearly have no idea what mental illnesses are.

I would only dream to aspire to be that good when defending an unpopular opinion. I assume his comments touched a raw nerve somewhere. Please rethink his viewpoint later.