This crap has been put forward way too many times. The thing is, this kind of flame happens everywhere, it exists, it has its roots somewhere, this is not directly the game developers' fault.
The thing is, Dota is supposed to be played as a team game where you have to work as a whole to achieve the ultimate goal - shortly put, a win. A problem arises when someone in the team stands out as underskilled, and everyone else obviously has problems coping with the situation as they feel, you are responsible for taking away their chance at a balanced game.
And Dota seems to be a game that can NOT be just jumped into, there are no prodigy players, people just play a lot to get better. I would argue that if you know where a head is and you can see your crosshair, you probably know how to connect the two and therefore play most of FPS games. It isn't that simple in ARTSs though.
But yea, they will make sure that you are coupled with ppl who should be quite similarly skilled as you, ofc matchmaking in parties will create problems as not everyone in a party will always be about the same skill level, and how would one go about finding a suitable team against them.
They will ofc be implementing the reporting system more so if someone is constantly harassing players, they will be shut down at some point.