So he didn't detain Bennett because he was afraid of him? Two problems with that argument:
First, what exactly was he afraid of? That Bennett would take a swing at him or steal his gun? Bennett was a public figure in the most public of settings (and the cop said in his statement that he recognized him). What reason would the officer have had to think that he would resist arrest? he had, apparently, already violated instruction and social norms.
Second, if he was in fact so dangerous that a cop (who presumably had some combination of a gun, baton and handcuffs) was afraid to confront him, wouldn't that be all the more reason not to let him run free? Not if the officer perceived Bennetts problems to be with authority, not his fellow revelers. The damage was done and over, or could very reasonably have been perceived as such.
For the record, I don't have any particular theory as to why the cop waited so long. I just think it's kind of strange, and would go a long way toward establishing reasonable doubt if the case ever goes to trial. Which, incidentally, I don't think it will. Unless Bennett is completely innocent and decides to fight the charge on general principle, he will plea down to some lesser charge and get a fine and/or suspended sentence. Which, based on what we've heard so far, is probably the best outcome.