Either way, you seem to believe that it is ok for Sony to do this because it is the fault of the computer user for allowing the rootkit to be installed?

No indeed, I do not. I am simply advocating for personal responsibility as the first consideration in maintaining one's computer (works well for other things too). Otherwise what do you have but a mess to clean up and the need to blame someone else everytime a new piece of malware (or even a simple bug) screws up your system?

By all means sue Sony but don't expect that to address the real problem.