The only response I ever get is "But the base will grow and margin orders will level off the volatility." Those arguments don't address my concern that a currency needs to have some psychological element built in like fiat does.
Your concerns provably don't matter.
By every objective measurement, adoption is proceeding exponentially despite every so-called problem. Bitcoin is already a successful technology because people are choosing to use it. Actions speak louder than words, and the actions of the market tell us that whatever issues Bitcoin may have none of them are deal breakers. Some of the flaws that various concern trolls want to "fix" are actually selling points.
If you're going to start out an argument with the premise that Bitcoin is fatally flawed then you're as grounded in the real world as someone who starts an paper on hydrology by assuming that water flows uphill. If you want to be taken seriously you've got to acknowledge reality first, then try to make the case that the gains could be even greater in some alternate scenario.