Here's a question - does it only cause ill-effects when it is used as a leave-in?
I use straight glycerin regularly all year round - in the shower. After I get my CO wash condish distributed through my hair, I put a good palmful of glycerin in with it. I continue to CO for a few minutes, then rinse out. Then I follow with another round of just condish. My hair is nothing short of awesome. I do this once a week.
I honestly have never used it as a leave-in. Maybe that's the issue?