https://www.crmvet.org/docs/otheram.htm
See the bit starting with: "Now there's another notion that gets out, it's around everywhere. It's in the South, it's in the North, it's In California, and all over our nation. It's the notion that legislation can't solve the problem, it can't do anything in this area. And those who project this argument contend that you've got to change the heart and that you can't change the heart through legislation."
To summarize it, he disagrees with you.
Can't take the mote out of your brother's eye until you remove the beam in your own. This applies to everyone, even anti-racists.
Notice MLK is talking about specific legislature, and the poster above was talking about electing officials. They are correct that merely electing politicians is neither necessary nor sufficient--the laws must change.
When there are sympathy protests outside the US, this is exactly what the sympathy protesters are attempting to remind you all. The US has nice ideals, eg "and justice for all"
"Even though it may be true that the law cannot change the heart, it can restrain the heartless"
I never read MLK much and just realized how awesome of an orater he was.
(I haven't visited the States since his presidency, but although I found much to dislike about the man, this is an argument I could get behind)