More often than not it will force him to define his hand while costing you less.

In this case we've gotten some information for only $6. If we were to check to the PFR who then bets $6, a c/r is going to cost us at least $18 and we still won't have anymore information than we would have had if we had lead out for $6.

I call the villains re-raise and check to him on the turn.