People online are awful, terrible people. 
 
However it seems to be worse with games like Heroes of Newerth and League of Legends.   
 
You have these snobs thinking they can boss everyone around and look down on those who do not do as good as them in the game.

There's voice chat?  Ugh.  I only ever got text abuse in that game.

Advice? Don't talk to people online. Assume that the players are elitist assholes, as most the talkative folk on PC are, and only respond to those who are actually friendly and helpful. I have not played HoN, so I don't know if there are any of those on there, though. I was thinking more for TF2 stuff, though the guys on there are pretty friendly compared to a lot of games.

People in this game always think they know best, even if they don't seem to know anything :P Anyway, never mind what people says about you in this game.
 
Some suggestions:
Play ranged heroes (easier than melee)
Buy marchers and a health pot when the game spawns
Be extra careful in the beginning, DO NOT DIE! 
Play with someone who can explain to you how to play :)

The DotA community is a little....intense.
 
And by intense, I mean assholes.

Look man, here is what you do, once they start doing shit, just piss them off on purpose and post "LOOOOOOL" to them everytime they get pissy, it's always great fun then.

If they get pissed at you just start doing it on purpose for your own amusement.

The Heroes of Newerth community is an incredibly elitist bunch. You can find some nice ones on occasion, but the majority of users are just intense about the game. 
 
Still, don't let them ruin the fun since when you start to get good at the game, it gets incredibly fun. Good luck!