Wow, well it was sweet he went there and supported you by going to your class. It is a tough subject to get into but at least he was honest. I hope all your fellow classmates and teacher were understanding and had tolerance for you and your grandfather, shit in the great depression weren't always pink with roses.

Sounds like somebody is racist.

As much as I understand why you thought an actual eye witness would be great, maybe just do the googling next time?

Especially when dealing with old people who just might go off the rails live in a situation like this, it would have been better to have recorded them - that way you know what you are getting before sharing. Almost everyone has a smart phone, tablet, or computer now. And I expect that your teacher could share your video to the class.