Let's be honest here. Trans people make up a very small percentage of the population (we're talking around half of one percent) so it's not exactly going to be something most people will ever encounter so having this standard is pretty moot.
That said, let's assume you do encounter a trans woman (and you're a man attracted to women), what are the chances this person is attractive? Pretty slim in my experience. You'll notice only the ones that are attractive will post on social media, but they're a very small minority (just like anyone else really, e.g. how many neckbeards do you see posting their faces on reddit vs someone attractive?). Once again, we've stopped before we even started.
Now, let's assume they are attractive, but if they're like most trans people they haven't had reassignment surgery. We've stopped before we even started again. I don't think we've encountered homophobia yet, unless you count not being attracted to male genitalia as homophobic?
Now let's address the small, small portion of the population who are:
They are still not the same. A trans woman's genitalia is not the same as that of a person born female. They have to do things to maintain it, it lacks natural lubrication et cetera. This can be just as off putting to people as someone who isn't trans but has some medical issues or whatever.