On the contrary, silencing voices is a necessary thing. All societies have to determine what speech is allowed and what isn't. There are lots of things you can say in general American society that will get you censured. Claiming that black people are biologically inferior to white people, for example. Claiming that women are biologically inferior to men, though? Some still seem fond of that one.

This all boils down to the fact one group is trying to add a number of new entries to the list of censurable topics. It's fine to disagree with that, but then you have to state a) what topics you think shouldn't be added to the list and b). why. When people walk around loudly complaining about how they can't say anything anymore without being specific as to what they want to say, it suggests that perhaps they know that those positions are not really defensible.

[EDIT: To explain things a little more. Societies must limit some forms of speech because some speech limits who can be a member of a society. "We should murder all Asian people" is not compatible with a society that contains Asian people. And no, it is not fair to expect Asian people to have to constantly defend their humanity to others who have nothing to lose in the argument. Much as it's nice to think about abstractly entertaining every possible idea, when some of those ideas actively push out or dehumanize members, the society is forced to choose between accepting debate on the idea or excluding those members. So yes, if you want to complain about how SV society shuns people for not wanting to experiment on human embryos or whatever, go ahead. But assuming that all ideas should be up for debate is ignoring the fact that some ideas are incompatible with your fellow society members. And you get to choose between debating those ideas or having those people in your society as equals. You do have a choice, but you can't have both.]