As a long time Dota player it is easy to see why people flame noobs who have never played before.
When you're playing a random pub and you find out someone on your team has never played before it's really frustrating. Because no matter what they are going to do they will feed and be generally useless to the team. You can't teach them as you go, there is too much happening. Either way you're stuck in a game for the next ~45 minutes that you are almost certain to loose and there is nothing you can do.
Your chances in Dota are better if the new person just leaves. That's why newer players get flamed. The team is better off without them, so making them leave helps your chances to win. Also when your team sucks its hard to do well. Games with lots of unforgiving teamwork and random ways of sticking people together who don't know each other are going to breed flamers. It's the nature of the game, if you don't like it don't play. The Dota/HoN community probably doesn't care haha.
Really? So it's frustrating to you that someone might buy a game, having not spent 4-5 years playing Dota to familiarize himself with the mechanics, and play in a pub match of all things? Sounds to me like you do care. That's why anyone who thinks that him/herself is a 'pro' will do his very best to get under any 'noob's' skin - but it's the 'pro' who is raging (omg, my win and k:d ratio wahhh) and all that, so 'ha ha' indeed, regarding who doesn't care.
The community is filled with incessant whining. One guy and his RL girlfriend (who were sooo pro! like, omg! they had clan tags and all that man!) accused me of ksing (a hero that I set up the gank for, PR ult gank request at level 6 etc.) and spent the rest of the game running around feeding the other team and trying to get me voted out.
That's a sample of the community, for those thinking about whether or not to buy this game. I've played less than 30 games, and each and every one has had some or all of:
1) Continual 'noob' accusations
2) One or more players doing something to deliberately mess up the game (quit, feed the other team, watch while you get ganked (and laugh about it on voice chat), or in general grief your teammates)
3) Incessant racist comments, comments about your lineage, your history, about how you fail at life, will never amount to anything, and so on, say, because you didn't spend the entirety of the first 10-15 levels buying wards and a courier for everyone to use (the same people who will watch you die and laugh about it)
4) And in general, nobody is trying (to do anything other than ks/have a good kill/death ratio, and/or to grief their own teammates).
I'd stay miles away from this game unless you already have friends playing. Even when there are 3 of us on the same team, 2 'pubs' can ruin the match (and often do so deliberately).
Oh, you might want to buy this game for 10 bucks simply so you can troll others - I'm sure that's what at least 60% of the player base exists to do.