Breaking someone's kneecaps is unquestionably a crime, copyright infringement for private consumption is not a crime, it's a civil offense (because listening to pirated MP3s doesn't make you a danger to society) so equating the two is a fallacy. I'm sure you already knew this since these arguments have been rehashed thousands of times over the past few decades.

I don't think you'd find much (if any) support on the moral angle either when it comes to people who genuinely can't afford to pay the asking price. I've never seen any authors, artists, etc. openly object to fans pirating their work in these circumstances but I've seen many of them openly encourage it. Seeing how you're equating the two, do you think they also like to have their kneecaps broken?