I feel like its hard to square our endorsement of hatred for enemies with the Buddhist texts, which instruct the opposite: to remove hatred and ill will, even towards bad people. One of the most famous quotes passed around is (from the Dhammapada) Hatred cannot cease through hatred. It can only cease through non-hatred.
I personally am still trying to figure out what I think of hatred, and whether (if at all) it should ever be accepted as an emotion for me to feel. You dont necessarily need to feel hatred towards your enemies to fight against them. Although I think theres a potential latent danger in destroying all feelings of hatred as a Buddhist monk might do, since youre more likely to forget WHY evil needs to be opposed or fought against in the first place. That hatred is, if anything, a reminder
Also, I feel like the Buddhist concept of karma disincentives people from carrying out our version of ahimsa. From what Ive gathered from the Pali Canon, karma is an amoral force, and isnt supposed to necessarily be fair (one of the many reasons why Buddhists want to transcend samsara in the first place). So you might be in a situation where you logically deduce that ending someones life is the best option, even a justifiable one on a theoretical level, but the act of killing always puts you in a bad mind state and accrues negative karma. So if you want to carry out ahimsa, then you must be prepared to make a karmic sacrifice and (likely) end up suffering in one of the hell realms when youre reborn
This conception of karmic sacrifice is probably how a lot of Buddhists justified participating in wars (including purely defensive ones). Im not saying that the law of karma is wrong or doesnt exist. I think its likely that the universe really DOES work this way. But I think it might sow doubt in a lot of people. Because if youre about to carry out ahimsa KNOWING that youll suffer immensely for it and be tortured in the next life, then youre obviously going to be a lot more hesitant than someone who follows a religion or philosophy where karma isnt really a concept. Granted, the Buddhist hell realms are temporary, but youre still supposedly there for a long time before being reborn again