Kneeling, on one knee or two, is one of the basic human postures, one which throughout recorded time we have invested with many meanings. The Wikipedia article below lists many common ones:
In that list there are: Respect, supplication, prayer, begging, petitioning or accepting an honor from a monarch, being ordained as clergy or knighted, surrender, proposing marriage, and so on. There is one meaning that has of late been attributed to the taking of a knee that is new and novel, indeed, unprecedented and at odds with all those others. That one is disrespect for one’s country and its symbols. That is indeed a strange reversal. Someone’s thinking is upside down.