Yes, he simplest solution would be to ban all boxes
not related to Wikipedia
or your activity on wiki (such as babel boxes). Though it's pretty easy to
tell what's divisive and what isn't (which, I think, is a reason to speedy
delete).
Pretty much anything can be divisive. Some things are obviously
divisive, but there are plenty of less obvious things that some people
will be offended by (often legitimately). To use the example already
given, supporting the US/UK/etc. troops in Iraq could very easily
offend those Iraqi's that are angered by the presence of foreign
troops in their country. It's all too easy to dismiss something as not
being divisive just because you don't personally know anyone that have
strong feelings against it. Because of that, it's best not to even try
and just ban all such userboxes.