Getting to the core of why it is Congress' responsibility to protect against piracy, is the little fact that it is built into the US Constitution. Article 1, Section 8 states that Congress shall have power..."To promote the Progress of Science and useful Arts, by securing for limited Times to Authors and Inventors the exclusive Right to their respective Writings and Discoveries;" That right there is the ideal our Congress is trying to uphold. The problem of course is that we have a clash of 18th century ideals with 21st century realities. In the modern world, copyright infringement comes largely from those seeking personal enjoyment or glory. Back in the day of our forefathers copyright infringement would have come largely from those seeking monetary profit. Besides, how do we define "useful Arts"?
I think to understand the full scale of this situation we need to take a little history lesson to see what our forefathers meant. We've all lived in a world where creative works are protected by law, but I wonder, what is a world without the protection of creative works like? I know I've never been taught such a thing even in college history classes.
In the end, what these acts boil down to is, do we wish to protect 18th century ideals, and continue protecting the profits of crappy mainstream music artists, and George Lucus, or continue on our path of free information?
Do we protect the profits of others, or the spread of knowledge for the greater good of humanity?