There's some research showing the opposite effect: escalation of good-deed-doing as one good deed leads to another. For instance, a classic study on the foot-in-the-door technique found that people who were asked to put a small "keep California beautiful" sign in their window were later more likely to agree to put a huge "drive carefully" sign in their yard (as an apparently unrelated request). This escalation could also be due to a self-signaling process, as people come to believe that they're the type of person who does this sort of thing.

Part of the difference is the time scale: the self-satisfaction of doing a good deed may fade relatively quickly, while the strengthened commitment to do-gooding persists for longer. That actually fits with Baumeister's view of willpower. He's argued that willpower is like a muscle: when used it tires in the short term but is strengthened for the the long term.

So it's hard to say whether involvement in symbolic do-gooding like church, Facebook groups, or political arguments helps or hinders the pursuit of genuinely important moral causes. They're not necessarily sinkholes - they could be useful practice, building moral fiber instead of wasting it. If you let them take over and you never do anything besides "practicing," though, then you may have a problem.