It sucks that this can't lead to conversations where people try to understand how this could be interpreted as offensive by p.o.c. as well as how a white person can make this mistake without intentionally trying to demean anyone. If we aren't allowed to have these difficult conversations, things will never change. Nothing good comes from absolute views, it only further divides us.
Greg clearly made a mistake, I don't think it's fair to use that to label him in any way. The most important aspect of this is that he learned from it and is going to try to be better. In the end, that's all he can really do. Hopefully, other people can learn from his mistakes.