By all means, cancel your cards and tell them why. Just understand that most of those apply to the sales side of things, not the purchasing side. That is to say, you can't use their service as a merchant to sell tobacco, prescription drugs, guns, knives, condoms, porn, etc., not that you can't use your card to purchase those items.
I canceled a Citigroup card with really good rewards because of a similar policy, but don't come across as an idiot when you're complaining.
