But the demand for a product is dependent on the supply curve, and with piracy, what you have is a zero-price channel to market, or a point on the supply curve that's at "infinity" quantity, zero price. In a perfect market, demand would be the total population of people who desire the product even a little bit, at the zero price point, with corresponding revenues of zero for the supplier. The reasons people avoid piracy add a couple of specks of demand elsewhere on the chart, be the reason honesty, convenience, price-insensitivity or fear of enforcement.
In a market with a zero price point, the aberration is that anyone pays for the product at all, not the other way around.
The presence of DRM merely increases the 'price' or decreases the ease or convenience of the piracy channel to market. It will therefore increase legitimate sales, other things remaining equal, regardless of the official price of the product. That's unless there are lots of people who won't buy software if it contains DRM, but I have my doubts about this argument, I think those people are way over-represented on a forum like Slashdot.
Trying to read people's opinions from the shape of a demand curve in the presence of piracy is not possible, it involves solving a multi-variant problem with only two pieces of information, one of which (number of copies pirated) is not accurately derivable anyway. What we're left with is a lot of people using fuzzy logic and presenting conjecture as fact. We cannot know, with the information available, the reasons for people's piracy, which is why the discussions on here are always the same - some people argue that it's all about price points, others argue that its about convenience, some say its about selfishness and an unwillingness to pay for things unless you're forced to, but really, we have insufficient information to know for sure.
As self-respecting geeks, we should be sufficiently adept at statistics to know what we don't know. Personal pet peeve : It would be nice if we could also be self-aware enough to stop presenting our personal opinions, decisions and reactions as in any way representative of the crowd, as so many posts here tend to do (not yours though!)