We have this discussion about every 3 months. I myself won't state my personal opinion since I don't think it would be proper but best I can tell the arguments are as follows, pro and con for the current policy:

Pro - the mods shouldn't need to babysit the forum with behavioral rules; this site is different from other forums in that there are no posting rules beyond spamming. The forum is "self-regulated" in that offensive posts, if considered offensive by all, are ignored or, now, muted. A general guideline not to "feed the trolls" in encouraged. There is also the dimension of not wanted to censor anything or anyone, because that can be considered too subjective, perhaps making the mods play more hardball with people they don't like personally.

Con: Offensive speech or hate speech should not be allowed on the forum, and some rules on it should be applied. Adding these the site's rules would give the mods power to punish those who break them.

Keep in mind that a great many people have "broken" the unspoken rule against vulgarity and hate here, but none have been acted against. Many of these people are still regular forum users and even regularly make slurs. The mute button was instituted partially to satisfy the con camp without having to actually regulate the forum.

Spamming and commenting on ongoing games/making cheating accusations however are strictly forbidden.