It's not in the least a Straw Man. As already stipulated, there was/is both racism and classism as part of the feminist movement - including the first wave, but holding people from the 1800s to modern standards and accusing them of things that they didn't actually do is unacceptable.

Anthony, in particular, was vocal about giving Black folks equal access in society at a time when Lincoln was talking about sending them back to Africa. Calling her a racist in the face of that is somebody serving their own agenda at her expense.

As already quoted in the original essay:

"Anthony expressed a vision of a racially integrated society that was radical for a time when abolitionists were debating the question of what was to become of the slaves after they were freed, and when people like Abraham Lincoln were calling for African Americans to be shipped to newly established colonies in Africa. In a speech in 1861, Anthony said, “Let us open to the colored man all our schools … Let us admit him into all our mechanic shops, stores, offices, and lucrative business avocations … let him rent such pew in the church, and occupy such seat in the theatre … Extend to him all the rights of Citizenship.”