So according to your logic, if a biological (aka cis) gay man doesn't want to date a trans man then he is transphobic! Seriously!?
People are allowed to have preferences. No one should be forced to date anyone.
If a person doesn't want to date people from certain ethnicity then it's totally fine.
It's only racism if the person thinks that just because he isn't attracted to them, then it means people from that ethnicity aren't hot or dateable and other people have the same mentality & attraction as his.