Although I agree with your comment that you need to not ignore the nuance behind subgroups, I disagree with you calling your parent comment racist.

These are hard questions and the nuance is not obvious to everyone. For example some people think my group (Arabs) all share common culture even though this is not true.

I think to be able to genuinely change things, we have to be careful about calling other racist. I will be the first to admit I am an ignorant. I think we're all ignorant about something.