The man was pretty obviously insane - at least by my definition of the term. Trying to find the reasoning behind the actions of a lunatic is not going to be very productive.

The church was white - at least the side which I saw in the photographic image was white.

Yes I know - you mean that the people who attended the church are mostly of the type called black, so it is a black church.

It is reported that 'the white guy' said 'you rape our women' but 2/3rd of his victims were women, at least one a grandmother. Perhaps he thought that he was killing lesbians. Who knows, but his actions were not those of a sane person.