I think you're going to have to own it - Your only other options are general-but-true vagueness - which is a bad idea since interviewers will either ask you directly or just assume something more negative to fill in the blanks. Or an outright lie - which is a bad idea full stop, lying on your resume generally has negative and serious consequences when you get caught out.
You state that you're "proud" of what you were doing during those two years, so it's a fair assumption that you still stand by the same political beliefs that lead you to be involved in the first place. That being the case why would you hide it?
Generally speaking most employers don't care what the political beliefs are of their employees - unless there's potential for harm to them as a result. Whether that's because it's something antithetical to what they do (e.g. an animal rights activist applying to work at a lab doing animal testing) or because of the potential for reputational damage resulting from the association if the role is a public one and the belief is a particularly distasteful one.
Presumably you're only going to be applying to work at companies that don't fundamentally run contra to your beliefs so as long as you're prepared for any potential questions as to whether you're able to commit to the job and how your political beliefs won't have any bearing on it I think you're good.