You can't disagree with something if you truly understand it?

Solving a difficult Work teaching:

The Work says, somewhere, that you can't disagree with something if you truly understand it. Really it means you can't be disagreeable with something if you understand it.

Example: when I first began engaging the works of Dostoevsky they made me very disagreeable towards them. I didn't like it. I wanted to throw his book (whichever one I was reading at the time) against the wall. I even stated that Tolstoy was mature and worth reading compared to this Dostoevsky. This disagreeableness was a symptom of my not understanding Dostoevsky. Then after these first initial encounters I began to 'see' what Dostoevsky was doing in his works, and I began to be able to understand and value them. I was no longer disagreeable towards them as a result.

But you have to also see it in an example of something you understand yet don't necessarily agree with. This is harder. Especially if it's something truly evil like Marxism. It's hard not to be disagreeable towards something truly evil. Yet that is not really a disagreeableness that flows from lack of understanding but from a natural distaste for the forces of darkness. Anyway simple discernment shines light on the difference between the two examples.