AOL was the Eternal September

https://en.wikipedia.org/wiki/Eternal_September

Some admins of private servers blocked its IPs for the same reason IRC mods did. AOL got ordinary people on to the internet, so they were a poorer fit for any existing community on average.

Once upon a time, cs.utexas.edu ran a well-known email-to-news (i.e. NNTP, Usenet) gateway. After some problems, AOL's admins asked the person who ran it to block AOL email addresses. Yeah, this was years ago.

Some time later, a person who had an AOL email account (who some of you might recognize, so I won't name names even though I'm dying to) contacted the sysadmins, complaining that the email-to-news gateway wasn't working. When she learned that AOL addresses were blocked, she threw a tantrum, threatened to contact various newspapers, complained about UT blocking public access to things paid for by public money, and so on. As a result, the mail-to-news gateway was shut down.

That's my AOL story.

There used to be tons of hacking tools for AOL, so I could see how IRC admins would just default ban connections from them to prevent hordes of script kiddies from attempting to cause chaos on networks they really didn't know anything about.