Some reasons for RPGs and MUDs being banned are that traditional MUDs are server systems rather than web apps, RPGs for the web tend to be heavy applications, they tend to be heavily trafficked, they tend to be poorly written and become security issues, the gamers tend to complain to the hosting company when things go wrong, they tend to get very spammy in their chat systems, and they tend to turn into command and control systems for malware if the people running them aren't careful and skilled. If you want to do something like an RPG, a dedicated server is really more appropriate than shared hosting.
As for parody, any decent US ISP understands the DMCA and copyright law. The DMCA forces them to forward the complaint and to take things down after a certain amount of time if there's no response. Parody protects you in the courts. The DMCA makes pre-court demands of the hosting provider. They can lose their immunity from copyright suits if they don't cooperate lawfully. Just be prepared to challenge takedown notices.
Other than a conforming DMCA takedown notice, any decent hosting provider shouldn't care as long as you're not a DDoS target and the content is lawful.
You seem to be more concerned about defamation than DMCA. HostGator for one won't do anything about defamation claims until there's a court order. They'll shut your account down if you are a frequently repeated DDoS target on a shared server, though. They'll do what the law says they have to do when the DMCA is involved, though.