I carefully read the two school proclamations you posted. There was no mention that the slaveholders were Democrat. And no mention that the troops who freed the slaves were Republican, and were lead by a Republican president.
I guess that was just an oversight.
Also there is no mention of the former slaves who petitioned to go back into slavery. They were not able to support themselves, they didn’t know how to farm, they didn’t know how to grow their own food. They had been fed and sheltered and the end of slavery was difficult.