It's not that government-enforced monopolies on copying or using certain pieces of information are never justified, just that they aren't property.
Your right to drive as indicated by a driving licence is not 'property', your planning permission for a building is not 'property', your FCC permission to use a particular part of the EM spectrum is not 'property'. And your right to make copies of a particular piece of information isn't 'property' either. These are all abstract legal rights/privileges.
If you drive without a licence, broadcast in a band reserved for someone else, or copy a copyrighted work, then you are 'driving without a licence', 'breaking FCC regulations', and 'infringing copyright', respectively. Calling any of those things stealing is inaccurate, which is the kind of mistake you end up making if you think of them as property.
Your right to drive as indicated by a driving licence is not 'property', your planning permission for a building is not 'property', your FCC permission to use a particular part of the EM spectrum is not 'property'. And your right to make copies of a particular piece of information isn't 'property' either. These are all abstract legal rights/privileges.
If you drive without a licence, broadcast in a band reserved for someone else, or copy a copyrighted work, then you are 'driving without a licence', 'breaking FCC regulations', and 'infringing copyright', respectively. Calling any of those things stealing is inaccurate, which is the kind of mistake you end up making if you think of them as property.