It's interesting that he kept interrupting you. He wouldn't let you respond, even when you tried. He also wouldn't say what he would do if you didn't move because he knows that if he threatened you unlawfully, he could be liable. If someone complained (which is questionable if anyone complained at all), all he had to do was tell them it was an open event, and that you weren't causing any trouble, and that they should choose to do a closed event next time if they wanted to regulate who shows up. (I wasn't previously aware of the laws on events, but what you said made sense, and now I think I understand the rules a bit better.)
I loved the smooth transition from an experienced street preacher to ignore the police harassment and just keep teaching.
Ah, there it is... so I was right. No one complained. He just didn't want you there. That's why he said he would go talk with the event organizers. If he had already talked to them, he wouldn't have to go talk to them again, especially since you hadn't actually made an argument for your being there yet because he hadn't let you make an argument. Since you were not allowed to given your reasoning, then what reasoning did he get from you to take back to the event organizers if he had already spoken to them? He didn't have anything, which means going back to the event organizers would just be a waste of time because they would have had the exact alleged conversation they supposedly had the first time. Again, the reason it doesn't make sense is because he didn't talk to anybody before coming over there, and it is very difficult on the spot, in the moment, to discern those things; I wouldn't have been able to catch it on the spot either.
If he was a good police officer, he should love the fact that you are out there teaching those things. You are preaching against the sins of the very criminals he has to arrest. You aren't doing any wrong, you aren't doing anything unlawful, nor are you causing any trouble. You are, in effect, helping to make his job easier, but he doesn't want you there because of his own sin, and after seeing that, I'm not convinced it had anything to do with safety or event coordination.
That last remark probably wasn't necessary since he was starting to move on, but what he said there was contradictory. He said you were disrupting the event because people were trying to eat and they were listening to you. Yet, he wanted to move you 20 yards away, which would not have prevented the people eating from hearing you; it just would have put you in a position to be heard slightly less, but nothing would have changed. So he TECHNICALLY did not tell you to stop, but his reasoning wasn't sound, so something else was going on that he wasn't being straight-forward about.
Nonetheless, it does not change the fact that he has no right to tell you to move without a lawful reason, and if you moved every time a police officer told you to, without question, you'd eventually just have to quit and go home, which, for some people, is their goal.
*SIDE NOTE: I didn't know you used to be an alcoholic. It's good to hear you got out of that, and now I know why you have such passion to preach to drunks.*