From https://www.marchforscience.com:

March for Science strongly supports diversity, inclusion and equality in science.

American and global citizens are best served when we build and sustain an inclusive scientific community. We advocate for equal access to science education and scientific careers. When evidence-based science and policy are ignored, marginalized communities are differentially and disproportionately impacted.

Scientists and people who care about science are an intersectional group, embodying a diverse range of race, sexual orientation, (a)gender identity, ability, religion, socioeconomic and immigration statuses. We, the march organizers, come from and stand in solidarity with historically underrepresented scientists and science advocates.