I've been hearing this same refrain from asian, african, middle eastern, chinese, and native writers for years now.
And I would say pretty much the same thing to them. I really don't like this idea, that you need a specific geneset/memeset to be allowed to write stories set in a certain place/time, or incorporating certain themes or mythological/folkloric characters. Not only because it needlessly limits people's creativity, but also because it ultimately just doesn't make much sense, since most people have ancestors from most parts of the world anyway. I'm pretty sure that most people in here have heard of the interesting fact that, apart from Martin Van Buren whose parents were Dutch immigrants, all of the U.S. presidents, including Donald Trump and even Hillary Clinton, are descended from John the Lackland.
Why is that? Because he was an above-averagely reproductively successful man who lived almost a millenium ago. Seriously, do those people have any idea how quick the human population growth really is? Any average person who lived just a couple of centuries ago, likely has hundreds of thousands, if not millions of living descendants today. Add in the constant migration of at least some parts of the society, and it's pretty much impossible not to have at least some foreign ancestors, for pretty much anyone. Not to mention that in the age of globalized media and the internet, it is not at all impossible to build a tighter link with a certain culture as a foreigner, than a good number of the people born into it have.
there is no white culture. Irish, Rhine, Slavic - no White.
Depends on what you mean by that. As far as I'm concerned, I would say, and I believe many social scientists would agree with me, is that while there are certainly differences between their various sub-groupings, white Americans are, as a whole, and ignoring a few outliers, a group distinct from the other European and European-descended groups, and since they usually just generically refer to themselves as "whites", you could say that their overarching culture is a "white culture".
white caste system. Not America right now, but Europe works like that.
Honestly, I can't think of anything better to say than what a person replying to those two people in that thread already wrote. (Un) surprisingly, the OPs did not respond:
It's not a "white caste system", for crying out loud! Americans just can't imagine people seeing world differently than they do, can they? The "black/white" dichotomy of American culture doesn't exist in Europe, it's about a million things other than skin color here.
Pretty much what I've wanted to write a lot of times myself, but never had much of an opportunnity. Anyways, to wrap this up...
Isn’t Europe the ultimate white society though?
In an ideal world skin color is meaningless, but in the actual world it’s all anyone talks about or refers to.
Nope. No, we don't. That would be a terribly empty way of looking at the world. I honestly feel sorry for you and the people in your social circle, if this is indeed how you see the world.