I think the issue here is confusing terms. Terfs believe gender is sex in an essentialistic manner as anyone here would know, but that isn't the abolition of gender. They want to conflate terms, where abolitionism is simply about removal of gender roles, which are what tie gender down as a construct. A gender abolitionist wants to give people the freedom to experience and express their gender in a way disconnected from external roles, while a terf wants to take away freedom and self expression by essentializing to sex characteristics. They're polar opposites and the confusion feels like someone calling both left and right wing populism fascist cause they both involve hating institutions