Personally I'd consider it more of misleading label than a slur.

[–] itsnotaboutewe 4 points (+4|-0)

I think it is definitely a slur. Humans can be divided into male and female sexes and that is it. By saying there are cis women and trans women they are saying there are sub-categories of females which equate to female women and male women. Breaking down female in this way is dehumanising and biologically wrong. We don't do it to any other animal on earth so when it is done to women it is a slur, whether the speaker intends it as such or not.