I've parsed it again a few times and I think you are actually wrong in your interpretation. It says the old liberals thought that by removing barriers to debate, they would uncover more truth. You've said the opposite, they valued the barriers.

And now that anyone is free to debate whatever they want, universal truths, religion, etc, not many people are interested in doing so because it has become considered bad taste.

That seems to be the gist of it.

It is a mystery to me why smart people find it difficult to convey meaning in a form that simpler people can understand.