I suspect that many on the left knew at the time Obama was lying about this but kept quiet because they really wanted the law to pass. They won.
[upvoted for giving a crisp recent, and plausible example of people getting away, at least in the short term, with dishonesty. I was a little squeamish about the politicization of the topic but I think it's hard to avoid giving a real political example in a conversation about political dishonesty]
I take the point that there's a complicated collective-action problem here where if enough people repeat something they wish were true, it can become relatively accepted, at least for a while.
The catch is that, as happened here, people often get caught having been dishonest. And we will see how painful the consequences are for those people personally and politically.
Scott, known on LessWrong as Yvain, recently wrote a post complaining about an inaccurate rape statistic.
Arthur Chu, who is notable for winning money on Jeopardy recently, argued against Scott's stance that we should be honest in arguments in a comment thread on Jeff Kaufman's Facebook profile, which can be read here.
Scott just responded here, with a number of points relevant to the topic of rationalist communities.
I am interested in what LW thinks of this.
Obviously, at some point being polite in our arguments is silly. I'd be interested in people's opinions of how dire the real world consequences have to be before it's worthwhile debating dishonestly.