another question to consider is how these hybrids would be treated in an advanced alien culture.
Probably the same way Mulatto kids were treated in the 1950's versus how they were treated in 2000.
I think it would depend on how long they have been part of the culture, but I think this is were an Antropology expert would probably be handy.
I took Antropology and just on Earth alone, people in different coutries, in real life, all treat different ethnic groups in different ways.
Heck you could even bring religion into it. Look at the Middle East, Muslims and Jews killing each other, and some of them may actually be from the same etnic background.
Hybrids would eventual become accepted, but depeneding an how their race views time, it could be a lot longer than the Human time scale.