You can hold the position that Hitler and the Nazis were evil while also believing US involvement in WWII was unnecessary and detrimental in the long term.

The history of Europe is one of unending conflict all the way back to Roman times. So what if Hitler controls all of Europe?

From an American perspective very little changes. Had Hitler not been beligerent toward the British and allowed trade with the US to continue there was basically no reason for the US to be involved.

Everyone would likely have been better off: 30 million civilian deaths could have been avoided, the iron curtain moves much farther east and millions more avoid the purges and starvation under the rule of the USSR after Europe us divided at the end of the war.

An alternate universe exists where Operation Barbarossa is successful because Hitler is not fighting a war on two fronts, and the USSR is either fragmented or controlled by Germany and the Cold War never even commences.

Additionally, Europe doesn’t become defacto occupied by the US for decades and atrophy to the point where half their cities are smaller than they were a few generations ago.

I personally don’t think such an outcome would have been better, but a strong argument can be made, and making it doesn’t mean you’re a nazi.