Here's an idea...
Instead of complaining to Poser users, who are going to disagree with you for obvious reasons, take your issue to the contest managers. Maybe you could request a contest that only accepts originally modeled creations.
What you're doing here is throwing the baby out with the bathwater. Instead of complaining about having contests that accept all forms of 3D art, and having those contests thrown out just because most of the entries use pre-made models, think beyond that into requesting some of the contests be for modelers only. That way everyone wins.

And you should also keep in mind that many Poser users do it as a hobby...and just don't have the extra time to model their own models. They shouldn't be kicked out of the art community (including contests) just because they have time contraints (ie: job and family)...or don't have the tools, or don't have the talent.