I watched this show, I was flipping channels and came across it. I probably saw the last half of it.
The crowd seemed kind of "hippie," maybe that is the kind of in-studio audience Cavett used to get on his show. A pan of the audience showed a lot of young people. It seemed like whenever Kerry was posed a serious question by O'Neill, he could make a quick joke at O'Neill's expense, get a pretty decent laugh from the crowd, and sidestep the issue entirely. O'Neill did get a good amount of applause for some of his comments, though.
In hindsight, knowing what we know now about the end to the conflict in Vietnam, Kerry comes across in some of his answers as pretty foolish.
The comment that caught my eye, which I haven't seen anyone else notice, is the one where Kerry opines that there is not going to be a bloodbath in VietNam when we pull it.