I myself do not have the social skills to message a member directly without being annoying/unfriendly/too direct/something else negative no matter how hard I tried (and I do try, even if it does not appear so!), but I know the moderators deal with this kind of thing often enough to manage it much better than I do.
No, they're not perfect, but they do try their best, and Dave will always have the final say anyway; this is satisfactory to me.
So, I feel more confident at punting it to the moderators to deal with, just like I do with suspected spam. I don't know if I'm right (about the rules, and a specific post actually is violating the rules), and am happy to have someone else to make such decisions, and be responsible for those decisions.
If I do not agree with their decision, I can always add that member to my Ignore list. (Which to me is useful, because that way I can limit what I respond to, and thus control my own output and way of interacting with others. Just because I cannot interact with them in an useful manner, does not mean they aren't useful and valuable to others. And in specific threads where there is minimal risk of that, I can still click to explicitly open their posts and respond in a positive/useful manner anyway. I do that a lot, actually, when it's likely they're helping others in that post –– that happens to override any personal bias or belief I might have, you see. Win-win, all around.)
(Banning is a much more complicated matter, when it comes to non-spam issues. Here, we're not talking about getting others banned, but just having them remove a detail in their profile or signature that is against the wishes of the forum operator.)