This is why massive marches and protests are complicated and sometimes a bad idea. I'm sure 99.9% of the women at the women's march had no idea who this woman was, and they were obviously not there to support that woman. They were there to express their distaste for the President's rhetoric towards women and to show some sense of unification.
It was also not just liberal women, it was women from all over the spectrum. The march was near where I live so I knew lots of people who were there. It was not just a collection of Vagina hat wearing Liberals that Sherdog has made it out to be. The people that I know who attended were very successful professionals, making 6 figure salaries, with a range of political beliefs.
They were not there marching alongside anti-semites, they were marching along with regular people. There were not large groups of anti-semites there demonstrating or anything remotely close to that. The Richard Spencer comparison the OP seemed kind of out of place to me. At Richard Spencer marches (like "Unite the Right") there are actually groups of anti-semites, KKK, white nationalists, neo-Nazis, etc, there demonstrating. That is an entirely different environment.