(this ain't all directed at you hog train. thought your comment was a good jump off point to give my broader thoughts)
It goes beyond even just what the KKK or neo-nazis did. It was society at large that used inclusion or exclusion from "whiteness" as a tool to reinforce racial hierarchy.
"white" has never been defined by anything other than exclusion, i.e., what it is not. Modern day dummies and liars pretend its just white-skin and that's it. But that is never how whiteness was defined. Irish, Italians, Greeks, Jews, were not considered white up until recently. Even still, none of these "pro white" grifters would include white skinned Latinos as part of "white" people. Millions of Asians have white skin - they're obviously not included with "white" people, right? What about all the white skinned blue-eyed people in Palestine and the broader Arab world? None of these pro-white idiots would include them in the group. So that term is still being used on the basis of exclusion. It has nothing to do with white skin.
There is obviously nothing wrong with being proud of your Irish/Italian/German/Polish/Nordic/French/English (ok this one is debatable) heritage. Hell, I'm a socialist/leftist with an "Irish Pride" clover tattoo on my ribs - not once has a single person raised an eyebrow or called it a racist tattoo. Not once, ever. But replace Irish, with white, on that tattoo - and yeah, now it suddenly would be a racist tattoo.
Celebrating/promoting your inclusion in a literally MADE-UP racial group that historically has only ever been used to reinforce racial hierarchy, is obviously deeply fucking racist to anyone that has 5 neurons to rub together instead of only 2.