Why are so many white people scared of becoming a minority? ?

If white people were genocidal, you wouldn't be here. So why are you such a GD liar?  When does the word personal responsibility enter into your lexicon?

Even when we are numerical minorities. We still won't get the benefits of being ethnic minorities. 

Whatevers.  It's a forgone conclusion.  The darker, dumber races breed like cockroaches, to make up for the high death rates from disease and starvation.  Yet they still manage to over-populate their portions of Earth, which are now spilling outwards like greedy locusts.

After that, all of humanity will be a version of brown anyways.

I'm not. I figure everyone is an individuals. But there are a lot of pale-faced losers who nothing to respect themselves for save their "race" (which doesn't exist, anyway).  Besides, the "White" group keeps expanding by allowing Italians, Jews, etc., to count as "White". Probably a lot of Hispcanic will count as "White" in another generation or so.

Because they're afraid they'll be treated the same way they treated other minorities.

Generally the darker the skin the higher the violence and lower the intelligence.

African negroes which are closer to Cro-Magnon man than Homo-Sapiens are further down the evolutionary ladder than American negroes because American negroes have been exposed to (although not accepted) civilized advanced white culture.

Would you rather live in Sweden or Somalia?

Not scared of becoming a minority in the least.  More concerned with minority value systems replacing our superior value systems simply because of overrepresentation.  

White people look at all these countries run by blacks and it scares the bejesus out of them, every one of these countries is a complete disaster with corruption going rampant...And exploding populations that they can't feed   

Because they're white racists who have bought into the fear-mongering coming from right-wing Trump supporting white racist extremists and decomposition trolls.  The rest of us, and especially those of us who have lived and worked overseas in nations where we already are the minority, know there is nothing to be scared about.

People like Tucker Carlson feed them a lot of fear-mongering BS.