Until bodies of government step in to crack down on these criminal groups, or society collapses to the point that we each just start shooting them when they engage in their shenanigans as individuals thereby preemptively terminating the worst offenders and leaders, there is no way to stop mobs from doing whatever they want.
No one calls COSTCO racist - or for that matter Sam’s Club. The reason is COSTCO and Sam’s happily accepts anyone who hands them the price of membership.
This would be the same - no one’s turning down black members...or members of any other racial group. Pay the membership fee and you’re in.
As far as a situation where a thousand thugs (of any color or race) shows up, the mall would just lock the doors. Fire regs would allow anyone to leave, but people could NOT get in without breaking down the doors. Most thugs know where the lines are - the lines between being a total jerk - and being a jerk who goes to jail. It’s unlikely thugs would kick in doors.
Besides, almost anything sold at a mall or Sam’s or COSTCO can be bought at other places. If out of control thugs protest they can’t buy sneakers - the names of non-mall stores that sell sneakers can be printed on a handout and passed out to ‘mall seekers’...