Except....'White' isn't a heritage, it's a social construct invented to keep those who WERE NOT 'white enough' down. I am, for example, a white man, but I don't celebrate 'white pride' because oppression isn't cool, and that's all 'white pride's is. Instead, I celebrate my Irish heritage, because that matters. Not my damn skin color...
If these 'white heritage enthusiasts' were just 'preserving their culture', they would be embracing Irish pride, or Scottish pride, or German pride, or Polish, or Italian, or...well, you get the point. Instead, they are 'preserving' a culture that has never existed, has no roots in anything but racism (we all know Black and Latinx and Middle Eastern aren't 'white' enough, but neither have Irish, Italian, Polish, etc been 'white' enough for most who claim 'white heritage'...).
The reason 'black' pride is acceptable while 'white' pride is gross is simple: black people, specifically in America, have had their racial and national and cultural identities stolen from them by slaves, who forced their slaves to adapt to white religious practices, white languages, white 'culture'. What we call 'black' culture has been built from the ground up by those who survived, and is thus, it's own unique-to-America culture, for good or ill, unlike 'white' culture, which only exists in response to the existence of non-whites.
So, yeah...'white heritage' and 'white pride' are absolutely rooted in racism in a deeply inherent way, a way in which SPECIFIC national/cultural pride is not.