It's doubtful they got fired just for that.
Per the previous poster:
Complaints against Varkey said he has engaged in "religious preaching, discriminatory comments about homosexuals and transgender individuals, anti-abortion rhetoric, and misogynistic banter" and that his teaching "pushed beyond the bounds of academic freedom with [his] personal opinions that were offensive to many individuals in the classroom," according to the letter.
Religious preaching, negative comments about gay people, airing one's own grievances against abortion, and espousing "men are better than women" viewpoints don't have anything to do with "teaching biology".
That's not to say that conservative leaning professors don't catch unfair blowback for certain topics for which their should be spirited debate...but it sounds like this person was going well beyond that.
For instance, if I, hypothetically, was a professor... and espoused pro-gun positions, and made statements about "Jews control all the money", and then when I was subsequently fired, tried to claim "they fired me for being pro-gun", that would be a pretty easy charade to see through.
There have to be other examples of professors getting punished for critiquing the excesses of the left on the topic of modern gender theory, but that haven't made those other kinds of petty statements along with it.
It'll serve conservatives well to pick a different posterboy for this particular crusade.