Yes, a number of politicians, mostly but not exclusively Republicans, proudly sneer at scientific expertise and wear their contempt for science as a badge of honor. But a march is supposed to show people how much popular support a cause has, and I regret to say that my feeling is that science as a profession doesn't have a lot of support today.
I think science and scientists have run afoul of a broader trend: the impatience and intolerance a lot of people have for doubt, or uncertainty.
We don't know where human society is heading. Wars are breeding refugees whose care is straining the ability of neighboring regions to absorb them. Global capitalism has displaced jobs for millions, rendering them near-refugees in their own countries, while governments seem to have reached the limits of the support they can provide. Cultural norms are being threatened as hitherto-marginalized minorities are demanding equitable treatment under the law. Influential pundits are portraying terrorism and loss of status as existential threats to their audiences. Other pundits, perhaps with greater reason but no less emotion, tell their audiences that climate change, resource scarcity and unmitigated pollution threaten our lives.
People simply feel overwhelmed by the uncertainty they face in their everyday lives. For many, the stress is intolerable. With their backs seemingly against the wall, they clamor for answers. They are ready to embrace anyone who says he or she has answers and the will to do what is necessary. They look to the certainties of the past for salvation. And they either don't have the ability or the patience to tolerate doubt: doubt, after all, either conveys uncertainty (the enemy of decisive action) or the possibility of error (the enemy of received wisdom, one of the crucial pillars for troubled people in turbulent times).
Genuine scientific inquiry, of course, always includes doubt. Measurements always come with margins of error. Theories are always subject to modification or replacement as new information comes to light or as better interpretations are found. Worst of all, it's rare that a single study or finding results in The Answer: just look at the whipsawing back and forth over the last few decades on what constitutes a healthy diet.
If politicians can make hay by ignoring and denigrating science (and they can, spectacularly), it's because millions can't abide its caution and care. Scientists aren't wrong by conducting their work with the caution they do. They are, however, thoroughly mistaken if they assume that merely saying "You should believe us!" in a march or on TV shows will address the forces operating against their profession. What scientists need to do is to make the public more comfortable with, and accepting of, doubt — if that's possible.
Otherwise they might just have to adopt the same resignation their doubters have, and buckle down for a turbulent ride.