Is the truth not the truth when told by a liar?

I've been pondering that since I read this post over at Mark Shea's, which was accompanied by this picture.

I have several opinions, often conflicting, about this.

The left has attacked a right wing mouthpiece using the left's most common tactic: ad hominem.  Whenever confronted by a message with which they disagree, they almost invariably attack the messenger.  In this case, the messenger has made it incredibly easy for them to do so.  Honestly, the man is a joke, and this message from him is sheer hypocrisy.  He has, through his actions, shown that he no more believes in the sanctity of marriage than does President Obama.  Obama, at least, is consistent. 

Even so, is marriage still sacred?  Is traditional marriage still to be upheld?  Is this liar speaking a truth, even if unwillingly?  Does having a ridiculous messenger make the message ridiculous?

The charge of hypocrisy is an easy one to make, and almost everyone is guilty of it at one time or another.  The world would be a very quiet place if all those who have at one time or another said one thing and done another were to never speak again.  Flawed messengers will be with us always.  If our message only has meaning if delivered by an army of saints, we shall never speak in a meaningful way.  We are not a Church of saints, but of sinners seeking redemption, and trying to bear witness to the Truth, even though we fail to live up to it.  Our truths will always be spoken by flawed, fallible, and sometimes hypcritical people.

And yet, the Left raises an important issue in this attack on Mr. Limbaugh.  Sanctity and tradition has left marriage in our society long ago.  Serial marriages, starter marriages, wilfully sterile marriages, cohabitation have all left their mark on the institution.  Right now, homosexuals seem to be the only group out there that actually wants to get married.  At this point, I would say, as I have said before, that homosexuals cannot debase marriage any more than heterosexuals have done already, of their own free will and by their own volition.

And here we are.  The folly with which we have treated the institution has become the greatest weapon against it.  It is in our weakness that our enemies are strong.