For the same reason that it's still controversial that chimps go to war even with not threatened. Some scientists see findings like this as an affront to their

For the same reason that it's still controversial that chimps go to war even with not threatened. Some scientists see findings like this as an affront to their closely-held beliefs about humans and human nature. And since these beliefs often have political implications, human tribalism takes over. What begins as a benign debate over, e.g. the validity of research methods, often devolves into controversy that's actually a proxy war for some tangentially related idea.