Did you mean species mixing? Which according to biology is impossible unless the two species are extremely close (ie. horse and donkey) and even then the offspring will be infertile.
Because race mixing means humans of different ethnic groups mixing, which is beneficial for our gene-pool and a really good thing for many other reasons too.
But Judy's mom never had a reason to abort Judy. She didn't have to worry about having to give birth to a fox mutant bigger than herself that is likely to be a stillborn or chronically ill She was a simple farmer who could easily pass her duties for her husband and elder children, not a celebrity cop. And most importantly: Wanted to have Judy and could offer a loving family and a safe environment to raise her.
Instead of asking who would have killed Voldemort if Harry Potter was aborted, we should be asking how many lives could have been saved if Voldemort's mother had access to abortions.