>"White people" do not have culture.

This is a rude statement to claim as you are denying the existence of a group of people. Just because a group can consist of other subgroups that does not mean a larger group does not exist.

>it's a social construct that exists primarily for exclusion.

Everything can be a social construct if you want to try and frame it as one and while the actual definition may be complex it is not any more complex than other groups of people like Chinese which also consist of subgroups which people may or may not consider the same Chinese as one another. To say that the term of white is used primarily for exclusion that is wrong and I think more reflects the kind of content you consume.