The problem comes in when they feel their opinions should carry weight about other people's kids. There are very limited ways in which we should allow that, and to an oversimplified approximation, they boil down to "don't do kids harm that prevents them from becoming an intact person society treats as a human allowed to make their own decisions". And then the problem is that some people think some websites do such damage, and other people think some websites provide help to survive such damage.