Early racists who used the theory to justify their beliefs weren't even aware of genetics as we understand them. They had a rudimentary grasp of the idea through Mendel's genetic studies but they grossly underestimated how complex heritability can be. (And epigenetics? Not even on their RADAR.)
Their understanding was so limited they actually used phrenology and took it for a "science."
Modern understanding of genetics has not only a far, faaaar deeper understanding of the mechanics of inheritance but it also has predictive power.
Can people use that for evil? Given that we could use a toddler's understanding of genetics to do damage so catastrophic some people won't even credit it as history, yes, it can be misused.
Fire, which preserved the lives of our distant Ice Age ancestors, can also be abused in ways normal people would never think up.
Any tool - and the understanding of genetics, like the understanding of fission, is at heart a tool - can be turned into a weapon.
Beyond that, Emily the primate, humans are not above the world; people are part of the world. And the more damage we do to everything else out there, the more will reach back to thresh humanity.
