What if I replaced "Online piracy" with "Gunshot deaths" and "digital goods" by "guns": Gunshot deaths are not a legitimate problem. It's an unavoidable side-effect of having easy and cheap guns.
Building and distributing on a massive scale, means that the whole operation will be illegal. Otherwise the state will make sure that you can only sell to licensed individuals and will also make sure that those guns won't be cheap.
To manufacture guns you need the materials required, like steel, wood, ceramic, ABS plastic and so on and you need to get them cheaply. To produce them cheaply you also need a heavily automatized factory that accommodates lots of processes like forging, stamping, milling, welding, riveting, casting and drilling. You can also outsource work, but to produce cheap guns you're better off controlling the whole stack. Of course, you could steal or buy those guns from the black market, like from the former Soviet Union arsenal, but doing so implies that you have connections and money to bribe people. Supply is also limited. And the risks are higher, since there are always people looking for those missing guns. So you're better off building your own factory, which of course has to be shielded from the local authorities (more bribes).
To distribute guns, you need a distribution network. And because illegal distribution is illegal and leaves traces, such a line of work is very high-risk. Like, you can always hire junkies to do the street-level distribution for a small price, but junkies are often getting caught by the police and then become valuable witnesses. Lots of mobsters got caught because of junkies. Also, if you want to cross the borders of a country with your merchandise, then things get really complicated. So if you want distribution on a massive scale, then it isn't going to be without a high price.
Compare to the Internet: communications can be encrypted with no way to eavesdrop without the key, it has very few single points of failure (e.g. DNS) and eavesdropping on peer to peer communications is a bitch, all this while copying and distributing has an absolute zero cost and can be done on a freakishly big scale.
4 days ago I wrote an article on my personal blog ~ 10,000 people viewed it in a single day, even though I'm a nobody. When you, as an individual, will be able to showcase your guns to 10,000 people in a single day, then it will be an apples to apples comparison (and you could use the Internet for that, but distribution and availability is location-dependent, you can't just click "download gun").
Downloading a file doesn't threaten anybody's life. Killing for the sake of killing is also not about money.
Before refrigerators happened, I'm sure there were companies selling ice to rich folk for a nice price. And if you lived then, I'm sure you could come up with all sorts of reasons for why refrigerators should be outlawed.
That being said, I agree that copying things should be legal, but not because doing so is easy. I think that it should be legal to copy things because I don't think people should be allowed to restrict what I do just because they want more money.
In response to your earlier comment ("...just because a crime is easy to commit..."), the right question to be asking is why something that's inevitable should be considered a crime at all. You might as well outlaw the water cycle.
In that light, the question is not "How do we stop the inevitable," but "What do we do to keep making big money in harmony and cooperation with the inevitable?"
EDIT: To the downvoter, you should probably take a look at:
first: they are both "unavoidable side-effect[s] of having easy and cheap" <something>.
second: they both might be bad. shooting someone could be good (maybe that person is trying to blow up a school). it could be bad (maybe the person being shot is just a random person off the street). online piracy might be good (maybe it encourages freedom or exposes government corruption or something). copying a file might be bad (maybe you sharing this movie with all of your friends makes it impossible for the indie director to make further more movies).
of course, you're also totally missing the point: just because something is unavoidable doesn't mean you shouldn't write laws to mitigate it. murder is unavoidable side-effect of human impulses. we should write a law saying murder is illegal.
i actually don't think we should pass draconian laws to deal with online piracy, but that doesn't make the argument valid. if something is bad, we should try and stop (or at least mitigate) it using proportionate and reasonable methods.
Wake me up when such methods exist. Right now they don't and politicians who represent a small group of copyright owners instead of a much larger contingent of content consumers are proposing bad laws to protect those who feed them.
The analogy also breaks because murder or theft deprive someone of something (in the case of murder, something irreplaceable) while content piracy only deprives content owners of a sale they most likely would never make.
Some of us who grew up in the digital world, and consider ourselves "citizens" thereof, want to see it allowed to develop independently of the arbitrary restrictions of the physical and political world. Regardless of the fact that servers and networks exist in physical locations, the actual subjective experience of using the Internet is like being in another place entirely, where those physical locations and borders cease to exist entirely.
I think you did the minute you made that analogy.
EDIT: fixed italics.