Eh, I have mixed feelings about this. I'm not sure why so many Christians feel the need to go into a gay community and do stuff like this. That is not how you convert or change anyone's mind. People, all people -- not just the gay community -- will become defensive and be less receptive to other viewpoints when they feel they are attacked. This type of grandstanding isn't really about changing hearts or saving souls. If you want to change hearts, you do outreach in the community that HELPS and show that you are concerned. That gives you an opening to share your faith. Of course, I say this as someone who doesn't really care if someone else is gay. I feel if they were born that way, God intended it for some purpose (and I don't believe in pre-destination -- so everyone has a chance to be saved) and I'll leave that between them and God. I do, however, draw the line when they are as bigoted and oppressive towards Christians or straight/cisgender people (like calling us breeders, etc.). I believe in equality -- not special treatment for them. But I do think things like the gay pride parade hurt them because the promiscuous, exhibitionist gays ruin it for the regular gay folks. (And for the record, I'm against the hedonism of Mardi Gras just as much as I am against the stuff you see in a gay pride parade -- so it isn't just because I don't like watching gay people make out or be half naked).
At the same time, I don't understand why gay people would feel the need to engage him, either. You aren't going to change his mind. If he is fanatic enough about the issue to be preaching it on the streets, he isn't going to be shouted down and convinced that he is wrong. Let him have his free speech and walk around him without acknowledging it. Don't engage. Don't even make eye contact. Pretend he is invisible. That denies the person the reaction they are hoping to get out of you. That should be standard operating procedure for anyone encountering someone who is preaching/protesting something you disagree with. They may have a right to say it, but they don't have the right to force you to listen or respond. They want attention. Don't give it to them.
But do I think he should be arrested? No. Free speech should be given lots of leeway. If he wasn't calling for violence or threatening anyone -- simply offending or bothering someone else isn't enough to give the authorities the right to shut down free speech. If it was about the loudness, give a warning and if he doesn't get the decibels down, then you write him and ticket and fine him. I didn't see any behavior that warranted an actual arrest.