He didn't want blacks attending his church. Christianity has a very long history of racism.
One aspect of the Trump effect is that these racist bigots feel emboldened to crawl out from under their rocks and self-identify.
Without even reading it -- Trump supporter. Now I'll reads it to see if I can confirm that.
EDITED TO ADD
Unconfirmed but I stand by my statement.
Who appointed him to be the one-man admissions committee of his church? Probably claims God spoke to him personally on the matter... Maybe karma will play out and he'll end up with a daughter that ends up dating and marrying a black man...