In short, boredom, character faults, if their short (and male this makes some try to overcompensate, after all look at Napoleon!!!).
Some people just like arguing though, that's the truth of it.
They probably don't have any real friends in the real world, so they come online, bored out of their head and let rip at anyone who replies.
I may to some who don't know me in the real world seem,(coughs) outspoken, for instance when in your case i pointed out the poetry you posted on the forum and claimed it as your own work was shall we say highly irritating to me, as i worked in publishing, and have seen plagerism before.
That and the photo you had up that wasn't actually you, well to me smacked of abject dishonesty and that;s why i spoke up about it.
It's not that i am passionate or have a deep seated or vested interest, it's just i like facts to be facts, and if i see a mistake, and can help to correct it i do....normally vocally!!!
As you'll probably remember if anyone lies i basically let rip, and ram the point home bludgeoning the person if they just don't admit their mistake, or just frankly lie or try to shift the blame onto someone else.
I admit i have a character fault, it's not believing lies when i'm tried to be told them and them portrayed as facts.
I hope i didn't bite you head off too much!!!
After all, anything you'll see on here is like old newspaper, it will be gone soon and may well be used to clean up dogs muck or diapers, so i wouldn't worry about it.
In short, who cares....take a break if it's bothering you, or in my case play online games and shoot the adversaries.
It realy isn't worth worrying about, honestly don't let any of the crap said on here bother you or anyone else.