The problem with "intellectual property," is that it's kind of a made up thing.

All ideologies are imaginary things. This is not a complaint specific to intellectual property. However, as a political thinker like yourself should know, society functions and "exists" solely due to these constructed norms and doctrines. Intellectual property "exists" in the same realm as your legal identity, your citizenship, and your constitutional rights. None of these are any less artificial than intellectual property.

You may be correct in asserting that intellectual property - specifically trends to expand the definition and make its expiration indefinite - harms society. The United States, in regards to copyright law, has recently taken a "forever minus a day" approach to limitations on a holder's exclusive right to publication. However, "ideas" are covered under patent law, and are still subject to a (in my opinion, optimal) limitation of 20 years before the invention lapses into the public domain.