I think you're conflating two different things. I'm also against intellectual property and digital monopolies on ideas or information. But breaking into someone's server isn't about copying information - it's about violating their physical infrastructure and their autonomy over their own tools.
The server is physical property that someone built and maintains. Breaking into it violates their control over their own equipment and destroys their work. This isn't about state-defined "property rights" - it's about basic respect for the boundary between your domain and someone else's. If I break into your house and burn your diary, the problem isn't copyright on your words - it's that I invaded your space and destroyed what you created.
I don't know or care if it's legally criminal, but it's clearly unethical. Your "data can be infinitely copied" argument would justify any digital intrusion - no privacy, no security, no boundaries. Anyone with technical skills could do whatever they want to anyone else's systems.
For me, real anarchism means voluntary cooperation and mutual respect for autonomy - not "whoever can hack wins".