Regardless of who created it, I've never seen a non-white person use it. My wife is Hispanic, and it has been offensive to her and her family.
I personally think that choosing 'x' was a poor choice, and it's basically unpronounceable by everyone in both Spanish and English. But making up supposed racist origins is a bit much.
Do you have a credible source for this claim? All I’ve ever seen are vague assertions it originated “organically” in the early 2000s.