That's fine. You don't have to go down infinite meta-levels of empathy.
You can just treat nazis like scum, and jerks like jerks. As long as you treat other people well and with compassion, you would still be behaving far better and more positively than how those who would make those supposedly "harsh, inhuman, uncaring, comments" are.
And you just choose who you consider "people" and who you consider "scum". It's like that old joke about Linux being user-friendly, it's just very picky about who it considers a user.
That position is shit, though.
Yes. That's necessary too. Did you rather treat everybody as an undifferentiated fog? Compassion is not about bending over backwards for jerks.
It's a problem when you're different from the Nazis only by virtue of "but I'm a good guy".
Being empathetic (take it from someone that believes they're an hyper empath) means understanding that if I were born in the 1910s in Germany and maybe blond and blue eyed, I could have probably been a big Adolf fan, but I was not, so current me believes fascists in general should get punched in the face indiscriminately and with extreme prejudice.
Having black-and-white thinking, of "I would never do that", like you seem to do, is proof itself of lack of empathy.
No, it's the opposite. I wouldn't treat anyone as an Untermensch because I'm convinced that the difference between me and them is a few throws of the dice. If you divide the world into "people worthy of empathy (by virtue of the dice showing X)" and "sub-humans to be treated like scum and vermin (by virtue of the dice showing Y)", you're completely sharing their worldview, you just randomly weren't born into their shoes and you don't agree with them on what the dice should show, but that's it.
That's not to say you should tolerate Nazis, but to not feel any empathy for them, and to not treat them as humans? Yeah, good luck on that road.
"Sure I tortured prisoners and waterboarded them ... but they were insurgents, and I'm a good guy, so it's all cool if I do it. Had they done the same to me though, wow, what a crime against humanity" has a super weird vibe to me. But it works, and Abu Ghraib documented neatly, how happy people can be while they torture others, if you tell them they're the good guys and that it's okay, because the others aren't really human.
Yeah, it's kind of like how Nazis killed people, and anti-Nazis killed people too.
So from that aspect they'd be the same. Besides, both sides also breathed, drank beer, and tied their shoes.
But the anti-nazis killed Nazis, not just anybody that they fancied for power, and they did it for freedom, and they didn't base it on innate characteristics (like being a Jew, or gypsie, or gay) but on bad behavior (like having occupied half of Europe, and burned people) and on stopping aggression.
So, yeah, there's that.