They don't make much effort to enforce other laws either, but that doesn't mean you should break them
Agreed, I just don't think that illegal and immoral necessarily equate. They usually do, but one does not imply the other.
I think the problem with the counter-argument in the article you link is that it assumes that if you download something, 1) you haven't paid for it earlier 2) you won't pay for it and 3) you would've paid for it.
People download copies of things they already own, people download to try before buying, and I think usually people download things simply because the price tag is high enough that they would not purchase it legally even if the 'free' alternative wasn't there.
It becomes a bigger issue when companies are actively profiting from this
e.g. premium usenet providers
Again, I am in full agreement. I wouldn't for a second defend folks who profit from other people's work.