Gary Yourofsky
Gary Yourofsky was (and in many ways still is) an immensely influential figure in the Vegan Community, and is credited with converting hundreds of thousands of people to Veganism. He initially started out his activist career by engaging in acts of civil disobedience, however, he eventually abandoned this method of activism in favor of an education-based approach. He gave lectures to tens of thousands of students, with some of them being recorded and becoming viral. His Georgia Tech speech is said to have converted 8% of Israel's population to veganism (from 5% to 13%), and this number doesn't even take into account all the others he's convinced all over the world (as his speeches have been translated into dozens of languages).
While Yourofsky has done more for veganism than almost anyone else, and has influenced many others to go into vegan activism, he is not without his share of faults... and there are many, many to list. While he has done so much for veganism, none of us here really consider him to be a particularly reliable source of information, especially when it comes to science and philosophy.
We can start with the good, but we really need to address the bad.