That's true, but I don't think climate change deniers/anti-vaccs are swayed by a march instead of actual facts.
If the actual facts would sway them we wouldn't have them. The march is also unlikely to make much headway with them.
The fact is, these people need a reason to change a deeply held belief that what they're doing is best in the face of louder voices. It doesn't matter that FUD may have been their initial source, it then becomes a matter of personal belief and trust.
The path to revising those beliefs isn't typically the repetition of "you're wrong," no matter whether or not that may be correct, and no matter if a chart or a mob says it.
Yeah, this is the real reason people should organise marches and demonstrations but people act like Trump is going to be remotely swayed with enough desperate dutch liberals on a field across the ocean.
Of course he won't. Marches in his own country
do have a better chance, but...this is Trump. I really don't think he cares, period.
What this
can do is raise general awareness of counterpoints to his stances. If those counterpoints are reasonable, and not well addressed by the administration, it could well undermine his support with that 41.9% that still approve of him.
The worst case scenario is that it will raise solidarity of people who care about these issues. Just the knowledge that you're not alone can be a powerful thing, and it may yet galvanize effects of its own even outside the political arena.
In that alone it's important even if Trump flat ignores it. Which he will. Real talk. I imagine he's already in Mar-a-Lago using the briefing to wipe away the aftermath of his morning Drumpf. But the march still has a purpose nonetheless.