The point being, I spend most of my disposable income on media of various sorts, but that doesn't mean I can afford everything I want - and if I can have it, why not? No one would be getting my money if I didn't 'steal' it, so the only person losing out would be me. The whole argument has been rendered redundant in my case by me not having a huge pile of cash to hand over in the first place. The RIAA/MPAA/whoever can take me to court for however many millions of dollars if they want - they'll get a lower percentage of my income awarded to them than I hand over voluntarily.
From a practical, pragmatic standpoint your argument makes sense. The ultimate issue, however is moral and ethical one. The argument here is that although you can pirate the media, you shouldn't because you don't have a claim to it as agreed upon by yourself and the other party (the RIAA, MPAA, artist or equivalent in this case).
The fact that the RIAA/MPAA/etc engage in abusive tactics is irrelevant in this argument, although many try to make it seem that way. It's essentially "two wrongs don't make a right". The actual idea is that you could pirate, but you shouldn't (or don't) because you have a certain moral or ethical standard about how to behave with regards to society as a whole. Assuming others follow your lead, then you will have culture where it's considered appropriate to deny one's immediate personal desires to ensure that everyone has an opportunity to benefit over the long term. The opposite of this would more or less be to engage in satisfying one's immediate desires regardless of the ultimate effect that this has on society in general. Assuming others follow your lead, then you will have a culture that is not interested in a stable whole so long as one's individual desires are accounted for.
Note that I haven't stated that one way is better or worse than the other. Society goes where it wants, and I think it's useless to apply such values as good or bad. You have to acknowledge the change that's taking place and either figure out how to turn it to your benefit, slow it down, or stop it. It's important to note, however, that this is the real crux of the "pirate/don't pirate" debate. At least, as far as I can tell. From a practical standpoint, there's really no useful argument against piracy. People have surprising moral flexibility, and if you can live with it and get away with it, then you will do it. And, since people (especially on Slashdot) will always find a way to get away with it, the question is, should you be able to live with it? If you believe in the "benefit society" argument, the answer is no, and if you believe in the "benefit myself" argument, the answer is yes. That's all. Any debate beyond that is justification and useless proselytizing. It really comes down to what you think is the most appropriate way to behave as outlined above.
I'm sure there are more nuances to consider here, but I think that's the crux of it.