What should I go to college for?

You don't need a specific degree to be an activist. So you can major in engineering, be involved in theater as an undergrad (if you can get a role as a non-theater major) and become an engineer-activist. Or you might be able to double major in political science and theater, but then your income in either political activism or theater is likely to be much lower. It's very difficult to double major in engineering and another subject because engineering is such a demanding major that many engineers spend five years earning their degrees in just that subject. So you'll have to choose based on your academic strengths and personal interests.

Well, then maybe you should do a double major or a major-minor.