Read guides, watch guides, watch replays, watch pros, practice against bots, over and over and over and over and over, until you have a pretty good idea of what's going on. Transfer the knowledge into the actual game then, and you'll be going places. We hate new people because it is a team dependent game, and if you're bad you just ruined 4 other people's game. That's how it works. I'm an asshole who hates new people too, but, if you're willing to learn you're generally a lot better off. The problem appears when you have new people come in and think they already know how to play, and won't take advice, and etc.
I.E. "I know how to play the game I've been playing for 2 weeks-1 month." No you don't, not yet, getting there, but not yet. It really takes months to like fully understand the game, and then maybe a year at least to really start getting good. It's a very time consuming game, and it's a very competitive game. Dota is more serious/competitive then say league of legends, so if you're really casual and are all about playing for fun, dota probably isn't going to be for you. It's elitist but it's true.
Good ways to start out, stick with support characters, the game isn't 100 percent dependent on your participation and how good you are then. Be a "ward bitch", you buy wards for the team as much as needed, and you place them throughout the ward spots in the jungle and etc. Everyone loves wards, and if you ward a lot, they'll like you a lot more. Good ways to learn characters are as I said above, guides, watch pros play them, practice against bots. The bots are actually really good, especially on unfair, their timing and reactions are measured in milliseconds. Good practice. You want to play as many people as possible, stay away from the more complex heroes at first like invoker, stick with simpler people at first so you can also focus on just learning game mechanics as well, like last hitting, denying, when to be cautious, MIA, map awareness, etc.
Play as many people as possible though. Don't stick with people just one hero because it's a fun character, There will be times when that character is a bad choice in a match, and you will suffer for it. Every character is tutored to fit certain roles and make certain counters. You also learn the abilities for all the heroes and that helps you a lot overall in terms of survival and expectations in team fights. If you really want to learn a character, stick with him for a few days if possible until you get him down enough, move on to someone else.
A lot of people don't completely mind new people as long as you're willing to learn, there's a lot of new people who aren't though, and that's when noobs get hate.