It seems to be the asssumption that comparing cultures and finding western culture superior is considered racist by many.
It may be that the use of the word "superior" is obnoxious. But I don't think it's necessarily a comment about race so much.
I admit that "western" is often used as code for white. And every bit as much in the sense of concealing racially-motivated criticism of whiteness as extolling its virtues.
For myself, I don't think the achievements of western culture are particularly about whiteness, and certainly not exclusjvely so. They are about a set of ideas (or roughly a set of ideas because they are also a range of them) that cohered (and continue to cohere) in countries we happen to call western, whatever the heck that means (unlike north and south, east and west are not terrestrial destinations, they are directions of travel).
And I see no reason why folks shouldn't be proud of the achievements of "western" cultures. It seems to me there's a relentless and widespread attempt to deny those achievements and only to find fault. To promote the notion that western culture is merely exploitative and not creative. To pretend it is exclusive and not to a great extent welcoming.
Perhaps this is one of the motives for the culture wars. That parts of the left often seem ashamed of the past of western culture. And parts of the right want to have no part in any sort of criticism.
Does anyone sensible claim the perfection of western culture? Nope. Not me, anyway. But that it identified with reason, valued and accumulated knowledge, generated democracy and the rule of law, developed modern science, imagined and executed magnificent artworks, spurred innovation and produced amazing discoveries, even finding a way to allow different forms of worship to thrive alongside one another, are all things which are valuable and aren't the products of all cultures.
I see no need for self-loathing. But that imperfection and change are a feature of the human condition are things I think I know. And that we strive to improve is another. But that we make mistakes and produce harms is also a universal truth. As true of us as of our ancestors.