Even if I agree with you that downloading an MP3 file is theft, that does not make it "pure and simple."
There's theft and then there's theft. One of the reasons laws and the sorts of distinctions they make are so complicated is because life and the real world are so complicated.
For example, even if downloading an MP3 file is theft, it is clearly NOT analogous to my stealing a CD from your home. If I steal the CD then I possess a physical object and can enjoy the benefits of such possession. Because of my possession you can long longer enjoy the benefits of the possession of that physical object. Etc.
So, Even if it is theft, how exactly is it theft? Even if it is theft, and theft is bad, how bad is it? Even if it is theft, what level of guilt would be appropriate if I do it? Even if it is theft, what would be an appropriate punishment for it? Even if it is theft, what measures are justified in attempting to prevent it?
If raising such questions annoys you, I sincerely apologize.
If calling it theft "pure and simple" is simply intended to be a discussion stopper, that's OK. No one is obligated to engage in or even be interested in such an (at least moderately) abstract discussion.
However, Although, the world is full of lying, thieving, self-justifying bastards, there is a lot of honest uncertainty on the part of people who don't fall into that category about the status of music files and the acts of making them public and downloading them. I take the regularly reappearing debates about the topic on Mudcat as evidence of such honest uncertainty.