I am far more likely to play with someone who has some losses rather than a ridiculous win/loss ratio. The first thing I want to do is find people with my general skill level and play for fun. Once you learn every trick in the game and win all the time, what is the point.
There is much bad behaviour in multi-player games but most developers took action in different ways to not eliminate but to curb it. I am a regular Battlefield 1942 and Battlefield 2 player on Moongamers. They will ban people for bad behaviour on a ladder. Warning, Kick, 1 day ban, 5-30 day ban, Permanently Banned. Swearing twice into chat is an auto-kick. With Steam games I could find and ban a person using the SteamID, no matter what they changed there name to. I want the option of not having to play with that player ever again. Once other hosts do the same you will find the punks behaviour changing for the better or not being able to play at all.
As to the point of multiple people using the same account, your number = your reputation. Don't let asses play on your number. The same could be said for loaning out your car.
As to the point that a couple bad apples can not ruin a community is hogwash. Look what happened to the reputation of the LAPD or catholic priests or any other large organization with some bad eggs.
Yes it Hurt the community.