I think the examples I raise of racism and homophobia are actually beliefs by your definition.
White supremacists believe in “racial purity.” They passionately support the idea that the races should not mix, irrespective of empirical evidence. Some white supremacists aver that white people are superior, but by no means all. It’s more an “is/ought” question that empiricism doesn’t touch on.
In that sense, it’s safe to say that most people find those beliefs unacceptable — because they harm innocent people for no purpose.
Homophobes and transphobes are much the same. While a few of them deny that sexual orientation and gender identity are biological phenomena, that’s not the case with most or all of them.
Instead, they hold to the belief that LGBT people should not express their orientations or identities. Is/ought again.
My proposition is that both belief systems (like some other belief systems) are morally unacceptable — again, because they harm innocent people for no purpose.