What's the name of the rhetorical tactic where you avoid an argument instead of addressing it by reframing the terms to create an obviously absurd and / or non-representative case?

There's a word for it, and it does not reflect well on the intellectual integrity of the people who use it. That's fair warning.

Back to the topic: I was speaking in generalities, but if I were to get as specific as you just did (by assigning a specific quantity of one), I wouldn't draw any sweeping conclusions before doing the intellectually honest thing by asking what happens when the quantity = n?

If, say, n = 1,000,000, then the effect is not so trivial. Moreover, the producer typically cares about the price point at which the number of sales and the value of each sale combine to produce the greatest possible revenue. While this point is not only non-obvious, it is likely to vary over time. So setting the price can be tricky. But one thing you can be sure of is that it's not zero. Moreover, all demand satisfied at the zero point is removed from the pool in which the ideal price / volume relation can be found, given that volume is a function of demand.

In other words, the optimal price in a leaky will pool will invariably be lower than one in a pool that doesn't leak. And that's how demand destruction lowers the commercial potential of a property with near-zero marginal cost.

Actually, the quantity could be one or it could be a trillion. When the price is zero, the demand schedule is pretty meaningless. I just used one as the quantity in my example because I was assuming that a single person would only download a single copy of a given good.

I didn't say that the effect of zero-price downloads is trivial. I said that you cannot conclude anything about the quantity of a good that would be demanded at, say $10, by observing that there is some quantity demanded at a price of zero. This was a direct response to your sentence "And yet, demand for that media was nevertheless satisfied."

> Moreover, the producer typically cares about the price point at which the number of sales and the value of each sale combine to produce the greatest possible revenue.

Greatest profit, actually, but you're pretty close. But I don't see your point. I'm not suggesting that all media creators should price their content at zero (although that certainly is a valid strategy that can and has worked).

> Moreover, all demand satisfied at the zero point is removed from the pool in which the ideal price / volume relation can be found, given that volume is a function of demand.

Not exactly. I have purchased media legally after having downloaded the very same media illegally, and it wasn't because I lost my downloaded copy. But anyway, this claim still ignores my point, which is that the fact that there is nonzero quantity demanded at zero price tells you very little about how much is being removed from the pool at non-zero prices. To use an obvious example, a person with zero disposable income can download an album for free despite it being impossible for him to purchase it at any non-zero price. Or to use another obvious example, I can download music at least 50 times faster than I can listen to it, and certainly faster than I could afford to pay for it. If I were to download a terabyte of music this week, that tells you essentially nothing about how much music I would be capable or willing to buy legally if I were unable to pirate music.

"this claim still ignores my point, which is that the fact that there is nonzero quantity demanded at zero price tells you very little about how much is being removed from the pool at non-zero prices"

But again, that's not the point. Indeed, asking about the amount of dilution assumes the dilution is taking place, and moreover, when it comes to artists and/or formats with established track records, demand prediction isn't a game of wild guesses. The ability to estimate, if not predict, demand is essential to the budgeting and capitalization of programs. So if you're aware that dilution is taking place at scale, you can approximate what you would have taken in w/o having to deal with the skim.