It’s a harvest festival, which is a venerable custom across diverse cultures. Ours happens to be attached to this particular event in Plymouth.
As far as “colonialism” is concerned — I’ll bet that all of these anti-coloniaists are open borders types that welcome any and all who come here but won’t admit that they are just more occupants of “stolen land.” The stolen land has become much more crowded since I was a kid. And I am including those from points south as well. An indio from Bolivia is not the same as an indio from New Mexico or North Dakota. If they want some hair-raising accounts of conflicts between the colonials and the natives, they should read the history of Mexico.
I am ashamed, but not surprised, that my alma mater is on the forefront of this. It was liberal but open-minded when I was there fifty years ago; not the leftist propaganda-mill nut house it appears to be today.
Southside, it’s a Puritan re-enactment of Sukkot. Which, yes, is a harvest celebration, but moreso part of our Judeo-Christian heritage. Going after Thanksgiving is actually part of the agenda of the anti-semitic left.