I don't take that from the gp at all. My perspective is that he seems to be saying you're not going to understand a position on an issue until you internalize it "as if" it was your own belief. By internalizing one belief and then another that contradicts it, you can truly compare them on the merits and perhaps become aware of the objective reality that they both share.

https://en.wikipedia.org/wiki/Thesis,_antithesis,_synthesis