While activists often feel like aliens, and sometimes are treated like aliens, in the way others question why we do what we do.
Recently, I found http://protest.net/activists_handbook/ It's a site that provides a handbook for activists. I encourage you to visit it, to devour it's many messages. Here's one of them:
"When people tell me that I'm crazy to work for others, I remind them that not all gain can be stored in a bank. I tell them that I can't live in this country with a clear conscience unless I'm working to make it better. I tell them that people I know are directly affected and I want this world to be better for both them and for my fellow humans. I tell them that the feeling I get as I realize that I'm changing things is a rush.
"Take a few minutes and think about what you care about, and why you do. Do so on the way to work, during commercials while watching TV, right now or any time you have a minute or two. It'll help you be more sure of yourself, and when you're approached with 'why do you do that?' you'll be able to answer. "