It is OK to celebrate our differences. Black people in the US shouldn't be expected to be white (or White, depending on your style guide). And the majority should listen to their voices, and not erase them by claiming we are all the same. We aren't the same. We don't experience the world in the same way, and we don't have the same shared history.
What are acceptable ways for white people to celebrate their differences and white culture?
Serious question . . . as I've always been taught that celebrating white culture is (at least mildly) racist and gauche since white people have oppressed other cultures through the majority of modern history. It's certainly possible to celebrate individual ethnicity and religions within whiteness (like being Polish, Jewish, Ukranian, British, etc.) but never whiteness. I'm actually struggling to imagine an acceptable way of publicly celebrating whiteness that doesn't come off as a little dickish.
Honest question- why do you feel the need to celebrate "whiteness"? As a majority ethnic group, to some extent, everyday is a celebration of whiteness.
Celebrating your heritage, not your race. When we celebrate Oktoberfest- is that not, more or less, a celebration of "whiteness"? Because Germanic heritage is white (although certainly not all Germans are white!). St. Patrick's Day in the US is a celebration of "whiteness"- because Irish heritage is white. (And again, this is not to discount black Irishpeople.)
As someone else pointed out, Black people, due to the history of slavery, has had their heritage erased. They cannot celebrate the country their ancestors came from, because many don't know. And as a collection of people, Black Americans continue to face discrimination their white counterparts do not. (As a group- sure an individual white person has been discriminated against, but as a group, white people do not face it.)
When we celebrate Black History Month or Hispanic Heritage Month, it's because, quite honestly, every month is white history month. By and large- the way our history is written is about white men. It's not because other people weren't there and weren't making contributions. It's because they were pushed into the background and not taught about.