It's a small faction of people that self identify as cissomething. Much of modern cultural discussions
are about language: what is "marriage" for instance, what does "gender" mean, what is "racist", what is "privilege". Asking people to give up and use someone else's language is unfair. In different ways respectable thinkers like Orwell and Chomsky say language is very important.
And I think the position being espoused but misunderstood is that people would like to take different approaches to promoting diversity (perhaps by being personally inclusive and politically neutral) but these sorts of codes of conduct are not conducive to those approach. It's not fair to say this is the way to improve the situation. Or that the situation can be improved this way at all. It may be shocking to people comfortable in American coastal culture, but this sort of thing is controversial (look at this thread!) and unnecessarily combative to people from other cultures.
Furthermore, it's not inclusive to many people because it takes a specific viewpoint in many complicated but intentional ways.