They are not actually organized, just common social orbits driven by an interest in activism of various sorts. They share a disdain for the "system" and the status quo and nebulous dislike for "injustice". They have enough differences (pet or hot-button causes) that some have or might splinter into different sub-groups.
They can't get a critical mass of people, because everyone has different top priorities (racism, feminism, LGBT*, environment, workers, peace activism, robot rights, and focused subsets of these).
The lunchroom argument / food fight in the community over the 2016 election between Clinton supporters vs folk arguing that their votes should instead go to Stein, or writing in Bernie, or just boycotting the election, remains legendary, and still has an impact among Juniors and Seniors in the community.
Gardner has conservative activists and advocates on campus, but are not considered ABCs and keep to themselves for the most part.