I'm all for open debate over the genuine science behind global warming - researchers who have research results that don't jive with the IPCC's consensus report should be free to present their stuff at real scientific conferences and not be ostracized just because their results are different.
But, as Real Climate points out, the Heartland Institute International Conference on Climate Change didn't even try to disguise the fact that it was a PR event, and not a scientific conference. The conference organizers invited speakers with this letter (PDF file), which clearly states that:
"The purpose of the conference is to generate international media attention to the fact that many scientists believe forecasts of rapid warming and catastrophic events are not supported by sound science, and that expensive campaigns to reduce greenhouse gas emissions are not necessary or cost-effective. " (emphasis mine)
There are big conferences which are basically promotional events (not necessarily a bad thing!) like the Bio-IT World Conference, but these are not to be confused with real research conferences like the Keystone Symposia or the Cold Spring Harbor Meetings, where the latest, and often unpublished research is presented primarily to other scientists, and not to the media or interested laypeople. And real scientific conferences aren't usually sponsored by organizations that have decided what the answer to a scientific question has to be beforehand (the Heartland Institute is specifically devoted to "discover, develop, and promote free-market solutions to social and economic problems" - I'm all for finding free-market solutions when they're feasible, but we ought to [gasp!] consider cases where the free market solution isn't the most efficient or beneficial).
John Tierny is having trouble understanding this distinction as well, implying that Heartland's advocacy simply counteracts government climate change-advocacy perpetuated by bureaucrats doling out funding at the NSF and NASA (never mind those pesky study sections!).
If you've never been to a real science conference, I suppose it can be hard to understand that, for all of the human failings that exist in science like anywhere else, there are strong institutional cultural mechanisms in place that make science work - like the fact that speakers at a meeting are chosen by a scientific organizing committee, and not by financial sponsors. Advocacy can play an important role in public policy, but research conferences aren't about advocacy.
(Real Climate has more.)