Many interventions in the economy have a positive expected benefit. (I should note that libertarians can concede this point, yet argue against interventions because they infringe people's rights etc)

Goalpost-shifting between consequences and virtues is characteristic of argument with libertarians, often in one argument with a single libertarian. It can be more infuriating than attempting to pin a Christian down on a claim.

Edit: Argumentative Internet self-declared libertarians, to be fair, per SMBC.