Animals and insects want things to be a certain way too. Why, then, aren't we locked up for swatting a fly or for running over a racoon?

Yes, superficially, values are subjective in that sense. We want there to be moral values, but that doesn't mean all desires are equally valid. Serial killers want to kill innocent people. Does that subjectivity morally justify their actions?

Or take the religious fallacy of mistaking the desire for God for God's facticity. The fact that we want something doesn't automatically ground that desire in philosophical terms.

The debate here is about whether humanism is philosophically justified. Which desires are best, and can we justify the presumption that humans have special value, compared to the animals we slaughter and enslave, with something more than the fact that we have that presumption? Are all presumptions philosophically respectable?

The fact that most folks don't think philosophically doesn't mean they don't presuppose some philosophical convictions in behaving as they do. Western individualistic consumers are generally humanists whether they realize it or not. We terraform the wilderness, and we depend on that revolt against nature. Deeds speak, and philosophers often just make explicit what we generally presuppose.