That makes it cheaper for people to argue against the information than to argue for it.

Not necessarily. It makes it cheaper for people to argue against whatever slim fraction of the information they can put up as a strawman without risking their own tongues. But it's hard to put up a real argument against an opposition that you can't really even quote.

And that increases that chance that people will finally consider him a liar.

Not if that strawman is easily blown away by whatever samizdat eventually conveys the full information.

Yvain explains some of the mechanisms better than I could in points 5 through 7 here:

http://squid314.livejournal.com/333353.html