@maporsche,
First of all, in the hypothetical you've posited, I would not respond " I think that ALL lives matter, not just black ones, but I include members of all races."
I probably would respond with "I generally agree with you and would love to hear your suggestions for how the situation can be rectified, but I hope you will agree with me that calling for cops to be killed is inexcusable."
If the person couldn't agree with me, the discussion would be over.
I've already stated that I think that ALM is an excellent rejoinder to people who can't discuss the matter rationally.