Im not hearing the whole story. For all we know she was disrupting class with the shirt, she goes home and tells her dad, who, by the way she's parroting, and right-wing nut dad decides to make an issue out of it. Judging by her age, she probably doesnt have any political opinions of her own anyway, and, save for a government class, there really shouldnt be any political discussion going on anyway, especially any kind of endorsing.
You make a lot of assumptions without any basis for them.
If we are going to make baseless assumptions, how about that the teacher just has an undying hatred for anyone white and was a racist? That's baseless as well, but seems ok by your standards.
"Racing is life. Anything before or after is just waiting." - Steve McQueen