Of course I support the idea of "off topic", but it is something that needs a lot of consideration and however one writes such a restriction, it's liable for abuse and probably has a zillion edge cases. E.g. is it off topic if I post "<your favorite politician> hates cat videos" onto a cat video forum? What if I am a moderator with <other side> political views, and I allow those posts if they come from people that agree with me and disallow them if they come from people who agree with you? What if I divide my site into multiple sub-fora, one of which is "politics of cat videos"? What if de facto use of my forum or a sub-forum becomes political discussion, but that everyone attaches a cat video to each post?
In other words, yes, I have thought a lot about it, but this warrants its own separate discussion.