Activism is defined by Merriam-Webster as “a doctrine or practice that emphasizes direct vigorous action, especially in support of or opposition to one side of a controversial issue.”
Note that it doesn’t mention age, race, gender, locale or scope. Activism takes many forms and can involve many people. Or it can be a solo action. It can be the product of a large, well-oiled and organized effort. Or it can be spontaneous. It can be big or small.