So, if we're going to use their criteria (dad's first, then mom's), Zero would be a black Caucasian. If you want to know how ridiculous white Hispanic is, just apply the same criteria to Zero, and that's what you get. Black Caucasian. It's an idiotic way to label, but for those looking for racism (as you say, they want the shooter to be white), no stone too small to leave unturned.
I know black people to this day who defend OJ Simpson and still believe he was setup by cops.
Now a situation like this where there are some grey areas, theres no amount of facts that are going to change their minds.