If interbreeding started to effect the existence of any race would it still be acceptable?
This is a very interesting question. I don't know how to reply to that but I can say I've heard that European and Asian genetic traits are recessive and African traits are "stronger".

I don't know if that's true or not, but if true that means that Europeans and Asian could theoretically disappear...
Only Caucasians would disappear. There are way too many Asians for their traits to die out. Whats kind of interesting is that Asians share a lot of traits with Africans so if everyone mixed the end result would be a race that looked like Tiger Woods probably.
If that were true would it concern you to know the white race would disappear
Not at all. There is nothing positive the white race in general brings to the table. Civilization begin without the white race and thats also how it will end. Its also actually genetically beneficial for the white race to cease to exist as we know it.
I get that Negroes still hate Whites (that's also what the Injuns call us/them).
But you have to remember there is enough blame to go around.
It was other African Negroes who enslaved opposing tribes of Negroes and traded them to Arabs for trinkets.
Then the Arabs traded them to the Jews.
Then the Jews traded them to the Dutch.
Then the Dutch traded them to the Spanish and to the English.
Then there were 250 years of American slavery (North and Central).
The part that militant Negroes forget is that a lot of Whites then died in a huge Civil War freeing the slaves, which war was triggered by slavery (according to U.S. Grant in his memoirs) but was about States seceding from the Federal Union.
Many including Grant wanted to relocated the freed slaves to Hispaniola (Haiti) because they could foresee Negro poverty and rioting in the future.
Congress however would not fund it.
Now we have Negro poverty and rioting with us forever.
And the latest scourge is the BLM movement of murdering cops.
Things just keep getting worse in spite of everything LBJ tried to accomplish.