/ My Polish wife's family hate me. Maybe it is because I'm black. Advice needed.
I understand your frustration and it is justified.
When I was young an old man at work told me "Oh you are Polish? Very resilient people. To retain the culture after all the hardship"
Poland was occupied for 163 of the past 240 years. Faced with Russification, Germanisation & outright slaughter (17% of Total Population in WW2)
Whenever I meet a Polak, it is an instant connection. We always share a common story of hardship and then our ambition for Polands future. Poland isn't just a place we were born, Polish isn't just a language we were taught, being a Polak is in our blood and the culture shapes the individuals we are today. For better & worse.
So imano, the previous poster and yourself cannot comprehend the hardship & sacrifice just like I can't African slavery
Are you Catholic? This is probably a big issue in your relationship with her parents. When I dated girls from Catholic backgrounds, it instantly brought gained acceptance from the parents.
Ultimately, her families blood line will die once you reproduce. The kids will not practice Polish culture (given the infuse of other cultures) and until/unless Poland sees a significant change in it's population demographic (like 75% White), the kids will stick out like a sore thumb. In Europe, multiculturalism was accepted if not even encouraged for the previous 20 years but those times are over. Non-European immigrants ruined it for everyone. There is now strong opposition growing to keep things in house.
Again, I'm sorry for you as I understand having previously dated girls out of race. But that comes with the territory. Most of this Globe is homogeneous. As the World becomes more globalized with social media, people enjoy being able to click OFF and return to their comfortable common society. Travel is affordable and open. If I want to experience an exotic culture I can board an airplane, I don't want the exotic culture outside my doorstep.
As Poland continues improving economically, this will attract more outsiders. But chances are you two won't end up living in Poland anyway. (For better & worse) you will take her to another country to raise your "Half Polish" kids. Unless your kids also have a Polish spouse, they will end up just like endless other "I'm part Polish" folks on this globe with no connection to Poland.