It doesn't seem to happen among people who play long time limits - at least in the year or so I've played here I have encountered no bad manners from any of my opponents.
Why blitz and bullet play should attract rude people I don't know. Especially if you are right that they are adults.
There is no problem though?
The problem is that you want everyone to be all goody goody & bestfriends with each other online. That is never going to happen. This is a worldwide website so obviously there is going to be thousands of conflicts here. Talking smack is apart of competition. If someone beats me in a close game, ill probably cuss at them too.
The problem is people like you, thinking that "talking smack is apart of competition".