Mr Kass would have done well to consider the words of the Democrat he quoted. Just as the Democratic party is an institution, so is the Republican party and both exist within the larger institution we call America. A logical extension of his argument is that we lock the Constitution which enshrined the  whole 3/5s dealie, ignored women, and functionally allowed states to restrict voting to males with property  away  but we don't- we marvel at how we have made it expand and move with our changes. We own the original failings - something the whole Confederate mythos misses by a mile.
The Democratic party has owned its failings as well and moved on. 
And the re-writing history dog whistle of his is just that, a dog whistle.