The problem is that this American morality is enforced to everyone internationally, as such a high portion of high-traffic websites are American. And it's not just about cursewords, it's this sick censorship of women's breasts, nudity and sex in general.
Communication on the internet is switching to a small number of mostly American social media websites like Facebook. If Facebook bans certain expression of thought or certain types of media/pictures, then that decision has pretty widespread effects. Even worse, when exposed to this kind of thinking, other countries will slowly start to adopt it.
On the other hand, other countries would enforce a different kind of morals more (like censorship related to racism and religion).
I love it when some sites make exceptions, like Tumblr (or Reddit in the past).