Maybe something that would represent a disbelief/repudiation/scepticism of the claim that trans people genuinely change sex. Would transsceptic work or is that still the wrong way around? Does the various origins of the individual words matter if they are words now used in english? Mis or phobic don't work in this case as it is not hatred in any sense. It is simply not believing/accepting as true what trans people are claiming. It is a case of not believing a man transforms into a woman by undergoing cosmetic surgery or taking female hormones or adopting attire now usually only used by women currently, in the west. Or using face paint. Or simply by saying they now identify as a woman.
Don't forget men in many places and (certainly in the past ) wear things like wraps/skirts and shifts). The Romans, monks, etc. Georgian men wore make-up. These things are just props. Fake boobies are just that, fake boobies. Being big chested or not is not what makes you a woman, so the employment of silicone doesn't either.
It just appears disingenuous to claim that GG's opinion is contributing to hatred, stigma and violence towards people whose opinion is that they have changed their sex. The campaign group seems to be vociferously the voice and concerns of transpeople born male who seem to want to stop a talk on feminism (and smear the female speaker into the bargain), because their claims are the most important thing and should not be disputed. No change there then.
She even says in that news night article, that she is not saying that people shouldn't become a transperson if they want. Just that she doesn't believe what they do doesn't make them a woman. Her opinion.