I haven't yet only because I don't know if they're under the mindset of black people needing to be saved by white people. It's never explicitly said, I guess just because I often see them with black people, or anyone who's not white, I just get that vibe at times. I think too because of history I'm always wary of that sort of thing. On a larger note I have a problem in general when the United States takes an ethnocentric view on other cultures, but that's a whole other rant
I respect people's beliefs but I do have a problem with trying to convert people, as you said it just strikes me as ethnocentric, but since that's apart of some people's beliefs systems, that they have to convert people to save them, I don't know how I'd go about it without offending someone.