“1. Using pirated software, you can produce the same stuff cheaper than honest people do.”
That's true, and I think everyone here condemns that sort of commercial piracy. I certainly do. But there are grey areas as well. Using pirated software, a learner can become much more familiar with a product — as David said, he might be more likely to buy a legitimate version of it or become an evangelist for the product. I know a couple of people who misspent their youth in a round-the-clock hypnotic trance with Photoshop, eventually to become talented and fully legitimate web developers/designers.
“2. You steal from the software developers as sure as you were taking the money out of their wallet, because they expect to get paid for their work, calculated their prices upon that, then see everyone use their programs and not getting any money back from it.”
But if they actually make more money through piracy, they're not losing money but gaining it. It's a funny sort of “theft” that leaves its “victim” better off!
“3. If the developers don't get paid, they won't make updates or a new version. Why should they?”
Having a lenient attitude to petty forms of piracy is not the same as allowing all forms of piracy, nor will it turn everyone into a pirate. As long as the bad forms of piracy are prevented, as they should be, developers will get paid. But anyway, creative people are not creative in proportion to the amount of money they get paid. They're creative as long as they can make a living out of what they're interested in. Public libraries did not kill education, home taping did not kill music, and lack of DRM in ebooks will not kill writing.
“4. Oh but not everyone is dishonest? Well, the honest (paying) users get to pay for stolen copies as well, because if only 5 copies are paid out of 20 actually used copies, those 5 paid copies have to bring in the same amount of money.”
We're all against large-scale commercial forms of piracy. But it costs money and time to pursue pirates. Presumably, there's a trade-off between spending a lot to pursue small-scale misdemeanors and just writing off the loss. Analogously, big department stores expect to lose an amount to customers returning unsellable items, and so on, and they have to make similar judgments about how strict they are with them.
“5. You are not “stealing property”, only a copy thereof. My standard answer to that is: in that case give me your credit card number and expiry date. That in itself has no monetary value; it's just a string of digits. Oh and it's fully ensured, so even if I took advantage of it (imagine!), you still won't have lost a penny.”
Getting someone's card details is not in itself theft. Before proper electronic security measures were introduced, it used to be the standard way of doing business. It becomes theft when it is used to take someone's money (including those who pay the insurance) without their permission. But that's theft of money, not theft of details. Analogously, using someone else's ideas with their permission, acknowledging their authorship, etc. is fine, but using someone else's ideas without their permission, not acknowledging their authorship, etc. is fraudulent. Whether we call it fraud, plagiarism, or whatever, it's very bad, but it's not exactly the same thing as theft. As I said yesterday, I actually think it's worse than theft.
I just think it's sensible to take account of circumstances, and to treat things for what they really are, rather than pretending they're something else. Advancing technology makes it increasingly easy to detect plagiarism, and pursue plagiarists — but let's prosecute them for plagiarism, rather than pretending it's theft!