Tasteless is good. Offensive is good. Stupid and offensive is still good, though clever, witty and offensive all in one bucket is the absolute best. Offensiveness gets people talking and thinking.
All that guff about tthese T-shirts, for instance. Yes, they are a bit unsubtle. But quite a few people who are now thinking, acting, stuff-buying adults are going to be a bit bemused by a) the existence of such t-shirts and b) the fact that other people are annoyed by them. To anyone who was born after about 1985, those t-shirts are about as relevant or interesting as a t-shirt that says 'Black Death, No Thanks' or 'Bring Back Pan's People'. Actually, those t-shirts are about as essentially important as assorted farts going on about how they've never met a nice South African and ignoring the fact that plenty of people who were born in South Africa fled from the place.
However, people's right to buy such t-shirts is important to defend. No matter how horrible you think the slogan on someone's t-shirt is, if you feel entitled to attack him/her the your own ideology and worldview has a fault or two in it.
Never forget, if censorship's the answer, it's a fucking stupid question. If censorship is being proposed as the answer, it's definitely worth asking what the question is.