I think the biggest misconception with trans people is that we "change from one gender to another" because we (as our biological gender) are gay. I personally identify as a gay transitioned male. I prefer sexual activity with other males.
I often get asked questions such as " If you like men sexually, why not just "stay" a woman?". I quickly go into educator mode , first explaining that I was never truly a woman, and that gender identity and sexuality are "two SEPARATE issues". Just as with biological males, females, Caucasian, African American, Hispanic Etc Etc Etc.. trans people come in all shapes, sizes, and sexuality orientations.
There are even transmen that identify as gay men and just so happen to have flamboyant type tendencies and transwoman that identify as butch lesbians. Then I might get a question like " Are gay men Ok being with a person who still has biological female parts?". My answer to that is usually something along the lines of "If the man isn't Ok with it then he's not the dude I'm usually engaging in sexual activity with!".
And the next question I'll get is "How do you engage in sex with a gay man?". My answer to that is usually something like "In the same manner any other gay man has sex with another man". Then I'll end up laughing and introduce discussion about the wonderful world of prosthetics. I'm real sure transmen of all sexualities get these same questions and I'm sure all of our answers will be a little different.