I think it’s due to not have anything better to do and because of that you get lost in your own thoughts. Slowly but surely you start questioning everything and than you look for someone or something to agree with you even if it’s your own subconscious. You start feeling bored so than you do yourself a favor and start harassing everyone else because your bored. Plus why wouldn’t you harass people online if they can’t do anything to you anyway. You can simply make another account and do some more harassing. In short lack of accountability is what causes some people to do stupid stuff, other reasons being their stupid or bored. Their are many reasons people complain about things but here in America people do it more than any other country I have seen.