Seeing how these people are censoring the opposing voices on their Facebook page, have you considered creating your own Facebook page to counter their scare tactics? I would suggest naming it something like "Save Timber Creek - The Open Forum" or something else to the effect that closely resembles the name of their Facebook page. Then maybe some of the people who are looking for more information on this matter will see both Facebook pages and get a better idea of what these course detractors all about. In your Facebook page make it very clear the reason why the page was even created. Express that unlike the opposition, all opinions are welcome and that you won't be censoring any of the posts. Use this medium to expose these people for who they really are. If you approach this situation with honesty and integrity then you'll come out the better person. If you can expose the censorship and scare tactics these people are employing, then the truth will make themselves their own worst enemy. Let them continue to spew their lies and nonsense but counter it with documented facts. Take pictures of work days. Show volunteers picking up trash throughtout the park, not just where the course is going in. In fact, your biggest ally would be seeking out park improvements that aren't even related to disc golf. Show an initiative that goes beyond just disc golf and you'll likely make a positive impression on those who know nothing about disc golf. These people who oppose the course will continue to villify disc golfers in their campaign. You need to show actions and words that counter their rhetoric. As unstable as some of these people sound, the good deeds of those supporting the course will likely infuriate them. Anger on their part will likely increase their assinine antics. This too will only serve to help your cause.
I'm not a Facebook fan. But in cases like this you've got to use the weapon of your detractors to level the playing field.
Just remember this. If you do set up the Facebook page, it must be honest, factual, professional and open to all (sans censorship).
Best of luck!