I understand your point but I would like to counter with a couple more.
First, Demo's are optional and they should never be used as a scapegoat to justify piracy. Personally, I think they should limit it to trailers, but thats just an opinion. If the developer decides to release a buggy demo, then it's up to the consumer to call them out on it buy not buying their product. Saying your going to steal because the demo sucked makes no sense since you're still willing to use their product, but you just don't believe you should pay for it. The value of a product has no correlation with the need to compensate them for it. If you think Mcdonald's has crappy cheeseburgers, it doesn't mean you get to eat them for free. I realize that software isn't a tangeable item, but the metophor fits. I realize it is extremely easy to acquire something for nothing in regards to software, but that doesn't make it ok. It just makes you a douchebag, even if there isn't anyone to call you out on it.
Second, I agree about faulty software. However, calling something "faulty" is very subjective because if it works as expected on even one machine, the software is valid. It might be poorly written, but that doesn't make it faulty, and thus this is a touchy subject because anyone could walk in a store and demand their money back because of faulty software without requiring proof. There is a reason they don't accept software returns these days.
People have a tendancy to be habitually dishonest if there are no real incentives not to be, which is the crux of the whole matter. For those times when they are called out on it, they act like they are 12 year olds who just got caught in the cookie jar when they know its wrong...making all sorts of excuses and justifications. They know it's stealing, because if they didn't why would they have excuses? Usually we get some witty philosophical diatribe about how it's not stealing because of X, Y or Z. The funny part, there are people that will steal thousands of dollars worth of software in a heartbeat, but the same person would object to stealing $10 dollars from someone on the street. People are so confusing.