As a science teacher I get very frustrated when I hear people arriving at conclusions based on incorrect information. Newspaper columnists, editorialists, TV shows, bloggers and politicians are not the most reliable sources for information. Yes they have opinions but their conclusions may be faulty and they shouldn't be looked at as experts when looking at scientific topics.
These people and especially courts look at problems deductively - you look at information to support your argument and do not put forward information that does not support it. We all know defense attorneys would not bring up evidence in court that would help convict their client.
Science works through inductive reasoning. Gather the evidence and arrive at a conclusion. Science is continually changing and conclusions are based on the evidence at that particular time.
Just because someone is a scientist does not he or she should be considered an expert. I would not go to my dentist to look at a broken leg.
Many of these global warming naysayers are picking pieces of evidence to support their argument from out of date information or from people who are not experts in the field.
Here is who I listen to.
Climate scientists doing current science:
http://www.realclimate.org/
Or the Royal Academy of Science whos members have included Newton, Darwin, Einstein and Hawking.
http://www.royalsoc.ac.uk/page.asp?id=6229
These are the experts not some judge who doesn't understand how science even works.
The experts are unanimous. Humans are affecting the climate.