I understand the point of this community is to highlight and shame bad posts, but I do wonder whether it would be better in cases like these to let the "meme" attempt languish in obscurity.

Your average uninformed person who doesn't vote is not going to see this and think "hey that's an interesting point". They're going to see this and think "wow that's racist". Spreading this further only serves to enrage normal non-racist people, make Jewish and black people uncomfortable, and give some validation to the original creator, who probably wants the knage to be spread.

Kind of like a poorly behaved dog or a school shooter: sometimes rewarding the behavior with any kind of attention only makes the problem worse.