In my blog post on my 10th anniversary at Ars, I promised to answer readers' questions. This is one of my attempts to do so.
Someone asked how to deal with a denialist/skeptic on scientific topics. I think the process can be best explained using a flow chart.
The first question is whether you’re dealing with a fully committed denialist. You’re never going to get Peter Duesberg to admit HIV causes AIDS or someone from the Heartland Institute to accept that we’ve got over a century’s worth of science behind climate change. So if your first answer is “yes,” then you have to think about whether an audience is present or likely to ever see the conversation. If not, then there’s no point in engaging. You’re never going to get anywhere with the individual, and nobody is going to benefit from the time you will spend trying.