How it’s deployed outside of that particular context (describing that historical period) is very different. It literally means white people, and has been used by violent terrorists such as the KKK.
Racists, authoritarians, and fascists purposefully, twist and misrepresent history for their own ideological ends, while accusing others who are actually writing good history, of doing the same, such as with Trump’s “1776 Committee” as a response to the 1619 project.
Probably, given that Irish has no k the C is always hard.
Talking of which it’s another word (Celtic) that I absolutely shy away from as it’s being coopted by Nazis. I mean I’m not saying drag down the Celtic crosses all over the country (because they have a meaning in their original context which is unrelated) but I wouldn’t be for putting any new ones up.