I assure you, those parents are not Trump supporters. Trump New Yorkers would simply send their kids private and laugh at the do-gooders.
What you are witnessing is the modern day, Twitter liberal - equality and diversity is the greatest thing ever, until it's your kid that has to give up his seat. For what it's worth, I actually do sympathize with them; I have two boys, six and three, and I'm resigned to the fact that I will have to pay for their education. The states that aren't super selective are absolutely awful.