Evolution provides another, darker use for objectifying people: the suppression of maladaptive mutations. If a mutation doesn’t favor the survival of future generations, it will not propagate. The easier we can spot someone with “bad genes,” the less likely we will mate and attempt to pass those genes along. There is a very basic value judgment involved, and it is grounded in long term survival of the species.
I would argue that this kind of judgment is acceptable, because it ultimately favors life. Unfortunately, we are far from good at it, because the environment we find ourselves in is very different from what we evolved for. For example, intellectual prowess, which stereotypically accompanies physical unattractiveness, may be far more useful for survival than it was hundreds of thousands of years ago. Also, it is one thing to be picky about your mate; and quite another to make the decision for others: racial prejudice and genocide, based on the misguided assessment of genetic fitness, are some of the greatest evils perpetrated by humans.
Because we are not omniscient about the future and how others can change it, the prudent and ultimately right thing to do is to value all life equally, and react to threats only when they are imminent and obvious. Whatever the causes for our ability to consider other people as objects, they do not justify our mistreatment of anyone.