Not only were they ruining people's Windows PC's with "security" software that leaves the computers open to attack, but they were doing it with stolen software!
Their malware uses code from at least two open source projects - LAME and FAAC. Under the terms of their open source licenses, anyone incorporating this code into a new product must release that product under the same open source terms. Meaning the original authors must be credited and source code must be made available.
Sony did neither. Making their software distribution an illegal act of copyright infringement.
Now we see the true hyprocrisy of the music industry. They scream bloody murder when you copy a CD for your personal use (which is legal in the US), but they have no qualms whatsoever about stealing other people's intellectual property when it suits their needs.