NAACP used to do this kind of stuff in the 60s and 70s.
One tactic was to send a Black couple into a predominately white community, visit a local real estate office and see if they could 'buy' a house. If they failed to get a negative reaction, they would find a pretense to leave without actually buying; if they succeeded in getting a negative reaction, they would threaten law suits. [Heard of Jesse Jackson's 'shakedowns'?]
"send a Black couple into a predominately white community, visit a local real estate office and see if they could 'buy' a house."
This happened to me many times whilst trying to sell condo-conversions in Shaker Heights, Oh. It really started to P--- me off, as I never failed to be as polite and as helpful as possible. I wanted a commission! After being targeted
several times, I found out the NAACP local number, and told them how much I appreciated their attention.