Several of them have been in the past.
I've always preferred to wear my hair a little long, when I was in elementary school the other kids called me transphobic slurs several times. To be clear, I am cis, but it still hurt seven year old TheLepidopterists's feelings.
The idea that expressing feelings other than anger is inappropriate for boys was also not great for me growing up, but the folks in the bell hooks book club thread have elaborated on that way more eloquently than I could.
EDIT: just realized this said cis-het which is only half true, but in spite of being attracted to men as, I've only ever dated women (I wasn't even consciously aware of being attracted to men as well until I was years and one kid into a relationship with my wife, who rules and is the only person I'm interested in a relationship with). I do present fairly straight though, I think and socially I'm I think effectively cis-het.