[ZenGum]

Some politically active people are motivated by an issue that does really affect them.

Some, by the need for some kind of mission or crusade to give their life meaning and purpose.

Others, by desire for power and egotrips.

The first might (but might not) have a good case, but the latter two may well choose any cause regardless of its merit. We are well advised to be distrustful of all of them, but we can't afford to ignore them all.