It seems to me that many people desperately want to believe that our ancestors were either vegetarians, or at most, scavengers and gatherers, because they view hunting and meat eating as "bloodthirsty," carnal, impure, "brutish," "savage," primitive, immoral, sinful, evil, etc. In other words, bad.

So they ignore the obvious evidence that's right in front of their eyes, and instead search for any nugget of information that seems to confirm their cherished hopes and beliefs. They start with the belief and then seek evidence to confirm it. Some of the people who do this, unfortunately, are scientists.
This is the opposite of the real scientific method, which basically starts with an examination of the evidence, as objectively as possible, then derives hypotheses from the evidence, tests the hypotheses, and then reviews the results. If the hypothesis is supported by the results, additional evidence is sought and additional tests are done to confirm and build upon the hypothesis and a theoretical model may be developed. If a hypothesis fails, alternative hypotheses are developed and tested and additional evidence sought. At least that's my basic layman's understanding.