So this is a psychological phenomenon that doesn't get used nearly as often as it could be, although it's very much in the realms of Saul Alinsky-tier disruption rather than anything that has real teeth. Still useful though.

I can't remember the name of the tactic or the phenomenon itself but when a person is speaking, if they hear their words spoken back to them directly after they have said each one, it disrupts their ability to maintain their train of thought and their verbal fluency.

I guess that sounds a bit abstract, right? But we've probably all been there when there's been feedback or an echo on a call or in a zoom meeting (where someone's speakers are feeding back into their mic so that when you talk there's a half second delay and you hear your own words just after you said them) and it just fucks with your brain.

You can harness that effect yourself and weaponise it against public speakers to disrupt and frustrate them. It's also particularly effective because they are likely going to experience a lot of frustration inwards rather than just experiencing people around them booing; if you can't even get your words out to finish your sentence then it's really kinda disabling and by making someone feel broken it really wreaks havoc on the individual on a psychological level. It's pretty unlikely to cause someone to have a mental breakdown but you can expect someone to give up and stomp away because they're so infuriated with themselves.

It may require a little bit of practice but if there's someone else who is keen to get in on the action then you can play around with using it on each other to get a sense of how to do it effectively.

The other thing is ensuring that you have enough volume to be heard sufficiently that the desired effect of disruption actually works. Doesn't mean that you necessarily need a megaphone yourself if you can project your voice or you have a makeshift acoustic megaphone made out of a stiff plastic sheet or some heavier cardstock or something similar.

Edit:
This is known as Delayed Auditory Feedback. Surprisingly, there's almost nothing out there on using this as a non-violent protest or disruption tactic so I feel like it was either something that was developed but never really given a label in protest movements or it goes by a completely different name in common parlance.

There's a knack to getting your timing right in doing this and it varies depending on the individual speaker but you can induce a lot of verbal disfluency that means a person might be reduced to speaking at a rate of like a word or two per second, meaning that they aren't going to get through much material and it causes a lot of stress in the speaker.

A more advanced tactic is, if you get someone on the hook with this and you're really fucking with them to the point that they are struggling to get their words out because they're focusing so much on your words, you can throw a curveball at them and say a word before they get to their next word to potentially derail their speech or even to get them to say the wrong thing.

As an example:

The Bible
The Bibe

Says
Says

Homosexuality
Homosexuality

Is
Is.. wonderful

If that makes any sense. By shifting from just repeating back what say to interfering with what they are about to say, it can really throw someone off balance. But they will need to get kinda sucked into your words for this to work. Confident speakers who are rapid tend to be more immune to this but ymmv.