As a player, no. For the same reason that I don't get mad at Cass for her comments at the Temple of Mythal. Faith is really, really important to both of those characters; in a lot of ways, it forms the core of their identities. So I can understand them being defensive and not wanting to think about the implications of what Coryflora says. Kind of like Sera's "LA LA LA LA" coping mechanism.
As a character, it drives my Lavellan absolutely batty. For all that Coryflora's nuts, he doesn't seem like the type to lie about something like that. Why would he? He thinks so little of you that taking the effort to lie about the Black City doesn't seem worthwhile.
Though I believe that Coprophages is not necessarily reliable in his memory of what happened...I mean, first, it happened hundreds of years ago...second, the dude is clearly crazyballs from the experience, his transformation/disfiguration, and his subsequent imprisonment. Despite the fact that his fashion choices are STELLAR, the guy just doesn't strike me as dependable.
I kinda feel he and the other guys got to the Black City, but when they found it full of insane elven gods instead of the Maker, everyone just kind of lost their shizz and went all sideways and corrupted. I mean, SOMETHING cast them out...so I don't really believe that he found the place empty.