Maybe include the second part of that paragraph i wrote:

That is why you should refrain from judgement over a human in his entirety. You can and sometimes should judge individual acts that you have witnessed or are proven.

But given the example of Hitler. Why is it important to consider the person in his entirety as evil? Aren't the intention and act of genocide by themselves an evil that needs to be condemmend and prevented?

I find Hitler and Fascism are great examples, because the story of the fascists being evil people is a form of "othering". They are the evil people, but we are not the evil people. This can all to easily lead to ignorance to how easily Fascism can spread and infect any people. And we see it in the way Germans wiggled themselves out of responsibility for their crimes after WW2.

To quote the Ausschwitz survivor Karl Stojka:

„Und das haben Menschen gemacht, so wie du, du und ich. Diese Leute kamen nicht von einem anderen Planeten. […] Es waren Menschen, so wie wir. Und nicht Hitler hat mich verhaftet, nicht Göring, nicht Goebbels. Der Greißler, der Hausmeister, der Schneider, der Schuster, der Bäckermeister, die haben auf einmal eine Uniform gekriegt, eine Hakenkreuzbinde, und da waren sie die Herrenrasse…“

And this was done by people like you and me. These people were not froma different planet. it was people like us. Not Hitler inprisoned me, not Goering, not Goebbels. [It was] the storekeeper, the house caretaker, the tailor, the cobbler, the baker. They suddenly received an uniform, a swastika armband and there they were the master race...

Or to say it with a caricature In Nuremberg and other places - "but he had ordered me to it":