Why are so many men uncomfortable around transgender women?

I personally love transgender women, far more than I do cisgender women. But it seems very few other men share this love that I have. I've always wondered why, and these are the only possible answers I could come up with.

They're insecure about their sexuality
They can't handle transgender women
Transgender women won't date them
Select gender and age to cast your vote:
Why are so many men uncomfortable around transgender women?
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