The fact is, he facilitated many frank exchanges of ideas. Whether he was willing to change his own mind during them is immaterial. Anyone could discuss any topic with him, and arguments needed to be made by both sides in front of an audience that observed and evaluated. Those sorts of interactions are the lifeblood of a pluralistic liberal democracy.
Imagine if Trump refused to debate for the presidency? That would be terrible, regardless of the fact that no presidential candidate would meet any of your standards for “good faith.”