I've had a similar comment...religious-based...I've got the "I just pray to God at night and tell Him that this is in His hands."
"You never had a rebellious stage as a teen, so this is you testing out your identity and trying to stick it to the 'man'"
"This must be because you spent so much time on the Internet."
"You were just shy so you never developed properly as a woman."
"You can't know who you are, because you are good with school, not people."
"Why would you do that when you can stay a woman and have hot lesbians eating you out?" -_-
My grandpa asked me once "what kind of woman would date you?" I asked him what he meant, and he said "Well, you know, lesbians? Other transgenders?" I actually answered him honestly, saying that I wouldn't want to date a lesbian, and they wouldn't want to date me once I am far enough in transition. But I said that I would date a transgender woman, because, well, they're women just like any other. Now he thinks I am a straight woman.
And a lot of people, in general, assume that as a transgender person I will only ever be able to date other transgender people. Apparently, no cisgender person would ever be interested in me. And the only friends I will ever have are other transgender people, too. It is very annoying.