It really depends on the league and the players in it.
The best way to increase your chances of playing with decent, good people is to get into a league with friends, family or even work. Then you know everyone IRL and know what to expect. You can talk smack and have fun without being mean and cruel to others. You can brag and not disrespect your other gms.
When you play with strangers, especially in Public leagues like ESPN, Yahoo, and cbs your chances of meeting cruel, mean and ignorant people increase. You can still meet some really fun, kind and cool people, but you also greatly increase your exposure to some Rude people.
Like with Facebook, when you comment in a public post. Somedays you get great replies and someday people attack you for your profile pic. If you stay in like-minded groups with good moderation and/or with family and friends on Facebook, your overall experience is smoother and you know what to generally expect with a lot less variables and random strangers.
IDK if that helps… But hope it did. Most people are good people even if they talk some trash or brag, but you gotta keep an eye out for the mean ones and don’t feed them.
Best of luck to ya sir