[pikma]

You can believe that gender is irrelevant and only sex matters, but you should still make an effort to be polite and nice to your coworkers - for example call them by the name they go for even if it is different from the one on their ID, use the pronouns that they prefer, etc.

Of course, like all things related to politeness, there is no absolute rule - if I change my pronouns every week I shouldn't expect people to keep up. But it should not be surprising that you can be fired for not making a minimal effort to be nice to your colleagues.