A property right is a positive right: it gives you the freedom to use, sell, etc. something you own. These are rights governments must protect, by preventing activities (such as theft or vandalism) that would endanger them.
A copyright is an entirely negative right: it gives you no new freedoms, merely the ability to prevent others from something they would otherwise be allowed to do. It gives one individual (the copyright holder) full control of a whole market (the sale of their writing). This is a monopoly, something governments must protect us from.
Copyright is not a natural right, but merely an outdated invention from the era of the printing press. To call copyrighted works “intellectual property” corrupts thought, by subjecting those who want to replace the invention with a more effective one to nonsensical claims of “you’re stealing my property”. To help you straighten out your thought and speech, I have a handy guide on terms to use instead:
Intellectual Property -> Intellectual Monopoly
stealing works -> restricting freedom
author’s right -> public’s need
rewarding creators -> promoting progress
taking other’s stuff for free -> telling others what they can write
as American as not stealing apple pie -> as un-American as placing Apple Pie Police in every home to make sure no one bakes one
(Thanks to old posts of Professor Bernstein for explaining this distinction to me.)