They're generally fine and you'll rarely have issues.
But when they're bad... they're really bad.
I agree with this 100%.
Most ALL of my pugs go well. But the few that were bad were SO BAD that it's painful. I've actually had a player find a way to "push my buttons" so thoroughly that I stopped playing for a few days. Later I calmed down and everything was fine.
It's like going to the park with my family. Most of the time it's awesomely fun. One day some )^%$# jerk keyed my car all along the right side. I told my wife, "I'm never going to that park again!" (I'm about half glad I didn't catch him doing it or I probably would have gone to jail for assault with a deadly sidewalk.)
Some people are terrible awful horrible people. It's just a fact of life. When they play online games nothing suits them better than to try and ruin someone else's day.