To be clear, this is my mother's opinion, not mine. She recently attended an anti-racism rally in Vancouver and had this to say about it. Eating cake is a reference to Tina fey's SNL sketch.
Things turned out as they did today for one reason -- thousands showed up and the racists were too frightened to come out publicly. Every single person who showed up to support anti-racism, immigration, and the Muslim community is a hero. If you stayed home shouting at cake, take a moment to realize that if everyone stayed home there would be no resistance to these hate groups and they would be strengthened and emboldened by your apathy.
