I never thought about it until now, but the best IRC networks I hung out on in the 90s were ones with really good net admins who enforced the rules. Even when I was younger, I didn't belong on certain IRC networks, and I was quickly banned from them. That same rule applies to all the other communities (mostly gaming) that I was involved with.

One problem with banning users is that they're not difficult to prevent from returning. At least on IRC, you had to pay for a BNC to change your IP address because whatever your dynamic IP resolved to, the hostname was fairly easy to reliably ban.