Yes can write anything as long as you abide by the rules. But if they feel that what you write will not attract any ads then they will put a dollar sign with a slash across it so unable to have ad revenue from that hub.
I have one hub that is like that because it has gruesome pictures of corpses and burnt heads. It's about the drug war on the northern borderlands of Mexico.
I don't think most people realize how many U.S. Border Patrol saves lives.