If that stage is in any way televised, I would spend no time addressing Trump and instead moving my gaze towards the audience.
Before the happening, which would surely be held a month or two in advance, I would do my level best to prepare a long list of mistakes Trump has made that affected his target electorate.
Given that I only have five minutes, I would pick the most juicy of those and appeal to these people's baser instincts, in order to present them with the evidence of Trump's negative effects on the country and reasons why these people should care about them.
I would look into addressing those issues on as personally-relatable a level as possible.
"That black cashier at your nearby grocery store. She works for minimum wage. Would your grown son who still lives with you do the same? Could he do the same? I think we both know the answer. So that black cashier is pretty much your main and only source of product that is within your reach that doesn't step on your comfort and the business of your life.
"Without her, you may no longer be able to get your produce, because no one else is willing to work for that little money. So far, President Trump..." – and would go ahead and attach an argument to it.
(That wasn't the best example, but I have not taken a month to come up with it.)
I would also make concetrated effort not to mention any of the core tropes of the political narrative of the recent times. I would not mention Democrats or Republicans, I would not mention Obama, Bush, Reagan, Nixon, or even Teddy Roosevelt, who seems to be a universally-accepted hero of the crowd. I would not mention Barr, Flynn, McConnell, or any other of the recent figures of non-news news reports, FOX style.
By doing so, I would seek to avoid engaging with the established mental traps that have been embedded into Trump's electorate's heads by the talk machines on TV, radio, or the Internet. Snapping the trap would only trigger an emotional response and prevent any further information from getting in.
Instead, I would do my best to keep to the story I want to present: that of Trump as an ineffective, counterproductive, malicious, corrupt president without mentioning any of those descriptors by name. I would treat it as a very short lecture, university-style, where I have to present information in a certain light for it to connect and start making sense.
No matter how seething I would be during this delivery, I would do my utmost best to remain calm, composed, and collected. Emotion transfers to the audience. People watching – at home or in the audience – will be able to tell that I'm angry and upset. More specifically, they will be able to tell that I'm angry and upset about something they've embedded into their personality. As such, it would seem an assault on their values to them. As such, I would fail very quickly if I don't make an effort to compose myself.
Addressing Trump has 0% chance of changing things. I've lived with a narcissist: any mention of ill results go past their ears that otherwise attend to everything.
Addressing Trump's core audience? 0.5%. The slimmest of chances.
Given the opportunity, I'll take the shot. It may end up changing something.