The claim is predicated on the mutual understanding that being a white nationalist is bad. If you lack that mutual understanding, there are bigger problems at hand!
There is no way to be reactionary without being a white nationalist and the two are interchangeable but you chose one instead of the other for some reason?
Sure. You can substitute “white nationalist” for “any kind of reactionary, including white nationalist” in my previous comment, if you find that more palatable.
There are certainly places in the world where there are significant local reactionary ideologies that are not White Nationalist, but the US is not among them.