it's taboo because there is no real scientific basis for one race being more superior. The differences can almost 100% be entirely traced to environmental factors like wealth, nutrition, nurture and community support.
No, we don't make things taboo because they're wrong, we make them taboo because they're dangerous.
Nobody is forbidding mention of modified Newtonian dynamics, just pointing out all the evidence against it.
The idea of differences in intelligence between ethnic groups, regardless of whether it is true or not, is not one that our society is currently able to discuss in a productive way. So, we very sensibly keep quiet about it for now.
I think it's taboo because certain segments of society secretly think there might be an element of truth and are disturbed by the implications and potential ramifications if the theory was proven to be true.
>it's taboo because there is no real scientific basis for one race being more superior
In which case it stands to reason that it's something that the things that make this or that race "superior" at this or that metric can be emulated by people regardless of race to everyone's benefit.
On your second point, I don't believe that is true. Not the 100% part. I am sure they play a big part, but a Kenyan Olympic runner doesn't win (only) because of environmental factors.