I think there is another agenda at work among the Clovis firsters.
The Clovis artifacts indicate a hunting culture that killed mammoths and giant ground sloths and other mega-fauna that went extinct approximately 10,000 years ago. By making the Clovis people the first humans to reach the Americas they can BLAME them for the extinction. This is the "Evil Human Beings kill off innocent wildlife" approach to history and ecology.
If, however, they were only members of a large population that had been here for millennia and mankind had lived peaceably with the mega-fauna, then humans cannot be blamed for the extinctions merely because it is human nature to extinct any non-domesticated animals in their vicinity. This does not comport with the accepted wisdom that all human interaction with nature is at nature's detriment.