It took me a long time to come to a wholesome concise response to this. The notion of "freedom of speech" within MassiveCraft is a bit ambiguous. The server is run by democratic westerners, and mostly played on by democratic westerners, which causes everyone to believe freedom of speech is a right all players have, but this is effectively not true. Full freedom of speech would mean you could call me a cockjuggling turdmongrel, and not face punishment or censor for it. In MassiveCraft opinions are free as long as they do not offend the server, the staff, any organisation related to or cooperating with MassiveCraft, or any particular player who makes use of any of the services provided by MassiveCraft. Additionally, if an opinion forces something upon, or away from any of the before mentioned groups, then we don't want to see it.
In the particular case of the subject, you made a very nonsensical post in the general with absolutely no background information. Because of that, people could not know that it was some sort of dramalama topic about Valyria and FHFDooM. You effectively forced the topic onto people who had nothing to do with it, or were actively avoiding it, and that's besides the fact that the post it was directing towards was rather inflammatory and hatemongering itself. If iko had made the post in general, it would have been "within the frame of acceptance" bar the fact it was hatemongering.
In the end, forum sections are for the designated topics. We don't want to see any cross bleeding like advertisement topics in general about strict-RP games or sales on the marketplace section. I don't see a need to add this to the rules, since it seems common sense to me, but correct me if I am wrong