why should you join?

Well, first of all it's fun! I can't think of a more interesting way to stay in shape. But it's not merely a physical discipline; there will be some book work. Some books are required reading and you will be expected to learn how to read and write some Chinese and Japanese characters.
And we can play some paintball. We'll show those wing-nuts that liberals aren't the ones who are sissies.

But on a more serious note,this country is more divided now than ever before. Hopefully our new president can bring us back together, but I don't know if it's possible. I am not an alarmist but I think it is a very distinct possibility that the streets may erupt in a civil war. The powers that be know we can't change the status quo if we are fighting amongst ourselves. They will pit the christo-fascist militia types against the people of color, and it will be secular progressives who get stuck in the middle. Like a jewish person in prison who can't fit in with either the gangstas or the skin-heads, reasonable people will have no time for anything other than survival. If I'm wrong and the worst doesn't come to pass, at least we can enjoy training in valuable skills and the comradery of like-minded people.