Sorry to draw away from your rant here, but they were asked to prove something didn't happen.
Nice try there. They weren't asked to prove something didn't happen, they were asked if they heard him say something that someone else confirmed. If I'm in a room with a bunch of people, and someone says something, I can say, "Yes, he said that." I can also say, "No, he did not say that." Nobody is asking you to make up stories, or words, so there's no "You can't prove a negative," going on here. "I don't recall," is certainly a possibility...especially if you weren't paying attention in the meeting. "I don't recall" means: covering for someone (where my money is, given the histories of Russiapublicans), they have terrible memories, they didn't notice the comment because they, too, are racist POS's or they weren't paying attention in the meeting at all. None of those possibilities would surprise me.