Is it religious bigotry to say, "I don't believe Jesus was the son of any god"?
Is it racial bigotry to say, "I don't believe Rachael Dolezal should be considered Black"?
Is it ethnic bigotry to say, "I don't believe you should claim Osag tribal status when ancestry.com says you have .01% Native American DNA but your entire family grew up thinking you were all Dutch"?
Is it ideological bigotry to say, "Flat Earth belief is demonstrably false"?
And, as any biologist will explain, human sexual reproduction is binary. We only have male and female humans. Even the minority of humans with DSD don't change the reality that humans are a 2-sex species, like most of all life, and absolutely all mammals.
If trans people claim to be a woman, they either don't agree with the majority on what that word means or they are wrong. They are not who they say they are. And this is very easy to prove.