A cop on the spot has literally only seconds to decide whether or not to eject someone; the lawyers and judges have months and years to second-guess.
What do you think of my idea of publishing the rules before the affair? This clearly would work better in an indoor venue than a sprawling outdoor affair. I tend to believe that most people will adhere to rules which they believe are not ad hoc and which appear to be applied uniformly to both sides. In other words, if it were announced that there would be no comments tolerated before the question-and-answer session, that might be observed without much police encouragement. If the police have to enforce it, at least it has the look of regularity about it.
I have no doubt that you and most policeman enforce order in these affairs not according to the contents of the speech but according to your judgment of the volatility of the situation and the threat created by the heckler. I have a problem with that though, why should a minority voice that offends the majority, even to the extent of running the risk of a violent reaction by the majority, be squelched by the police because the majority is on the verge of committing the crime of assault? I know what the practical answer is, there aren't enough cops to control the majority that they can control a single heckler.
Even more difficult for me is a situation in which a heckler is suppressed by the police not because the crowd is on the verge of violence but merely because a segment of the crowd is offended by the content of the heckler's speech.
From the policeman's point of view, he is there to preserve the peace as the first order of business and not to act out hypothetical constitutional free-speech scenarios.
We often hear that the people in the audience have the right to hear the speaker but can it not be said that a heckler in the audience has an equal right to make his voice heard over the speaker? The audience will say they came to hear the speaker, but the heckler can say they came to be heard. I know which one the cops will favor and usually they will be right to favor the speaker over the heckler but that assumes that the speaker has some paramount right to be heard. This takes me back to the original questions about who was sponsoring the affair and who has established the rules originally?
With all these imponderables it is small wonder the policeman's lot is not a happy one.