To me what is therapeutic is when the truth is spoken - and by this I don't necessarily mean the person even knows what the hell they're talking about, but if they really believe something that's a truthful expression of what they think. Its refreshing to have that kind of honesty.
Of course, the nice thing about having a dialogue is that someone may point out something you were not aware of before, and if you are interested in the truth you will appreciate that, even if you think it makes you look bad. Frankly I think when we deny the truth on any level, that's when you'll have some kind of mental dis-ease - it's really a simple principle. If you're honest with yourself, finding that truth will be a relief, like a load taken off your shoulder. There may be other intense emotions over having been in falsehood all this time, but I'm sure atleast some have experienced that relief from being in confusion.
Frankly it's a matter of integrity. It's one thing to believe a lie, it's another thing to live it. Often the relief comes when you see the truth about how you're living a lie, and you can finally relax and stop tearing yourself apart over a way of thinking.