you're forced to hold the position that Hitler's actions weren't morally wrong
Jesus Christ, what did I
just say? It's this: "Where the hell are people getting this idea that morality being subjective means that you can't have your own personal standards?"
I
believe Hitler's actions were morally wrong, because I'm judging it according to my beliefs. He didn't
believe his actions were wrong, because they're according to his
beliefs. Both of us would act on our beliefs, which is to say, he would try to carry out his fascist plan, and I would try to stop him. All of these things are objective facts, and if you're trying to base your actions on the belief that there's something else happening, you're going to fail.
You'd have to look at philosophy for that.
Philosophy isn't a real area of study. Psychology is. There's a reason moral relativism is a "fringe position" among philosophers, and it's because it'd put them out of work - after all, philosophy is a capitalist practice, and philosophers need to make themselves useful in order to get even the
slightest
bit of work.
Sorry, but I'll take the field that uses observable data over the one inspired by Greek guys bullshitting. I mean, you do realize almost all the ancient philosophers were also hypothesizing about things like "what the universe is made of", which is a field that we now address with science? We don't pretend like the universe is made of fire, like Heraclitus believed, or that the sun orbits the earth, like Ptolemy believed. Why, exactly, should we put our trust in
philosophers
when they're a field that has always historically been based around having zero evidence?
Anyways, good luck convincing people to become vegans if your only policy is shouting THAT'S OBJECTIVELY WRONG at them.