It is wrong to troll others.
John enjoys participating in the comments section of youtube videos and sees an opinion of a video posted that he does not agree with.
John wants to respond to the opinion.
John replies to the comment, laying out a well-reasoned case for why John has a different opinion.
John replies to the comment, calling the other poster a big dumb idiot and telling them their opinion sucks.
The other person counters with reasons of their own, and a long and engaging conversation ensues.
The other person feels stressed because they're being picked on over the internet.