Maybe aliens are real.
Maybe they've already been here. Maybe some still are.
Maybe they don't look any different than us. Maybe they don't have big heads, weird skin, and big bulgy eyes. Maybe they look just like us. Maybe they're the same inside and outside. Maybe their blood is red. Perhaps they have a few evolutionary traits that are more or less advanced than us, but maybe they're able to blend in as "specially gifted." Maybe some humans can do those "special things" too.
Your best friend could be from another planet. Maybe you are. Maybe your parents never told you that you cam from another world. But you don't seem too different, do you? You look like humans, you speak like humans, you act like humans...
Maybe life forms on other planets aren't much different than us. Cultural differences, maybe, and perhaps the progress of their civilizations, are slower or faster than ours.
What if an entire society is from a different planet, just fitting in with us? Maybe France is from another planet. Maybe Australia is from another galaxy. Or maybe Canada and India are both from the same solar system.
Maybe America isn't native to Earth. Or maybe certain races aren't really human.
You might marry someone who's really an alien. You might have kids with them. But you would never know what they are because they're so much alike us. Your children would only be half human.
So what if this was all true. What if you found out your closest friends, be white, black, Mexican, Asian, Indian... or French, Irish, Canadian, Persian, African, Samoan... What if you found out your wife or husband, the love of your life, wasn't from Earth?
Would you treat them differently?