frankly, some people take offence when they get flamed. If you have a valid point it's better to reinforce your argument than raising your voice. Also being humble makes you a better person.
If you read newsgroups long enough, there are a lot more stupid answers than, stupid questions. You just have to use your better judgment. More or less it's OK to cross post only if the topic applies to both groups. Some people don't like to reply to cross posted groups. I guess they feel like spam bait or something. Who knows, who cares?
As for this NG, if it's Z related, it good to go. At least in this NG, there aren't many NG police, unlike other groups I read. They get mad when you top post. Like who made it a crime to top post?
Cheers! JW