Well, I am not sure we should unless we want to subsidize the production of more ideas and opinions than can be produced without subsidy. And the evidence is that we produce far more ideas and opinions than the market will bear.
Propertarianism says the opposite: that you may not sell those ideas and opinions without contributing a percentage of the income to the author. We call this the Creative Commons license. Which is that creative products cannot have commercial use without compensation, but have free use for non-commercial use.
This strategy does not violate the test of productivity or parasitism.
This would have an enormous impact on the publishing industry, all of which would be for the better.
One of the reasons, if not the most important reason that we have sh_t art, literature and cinema, is that the creative subsidy of copyright protection shifts the quality downward.
This is what I object to, and I consider immoral.
I do not consider individual cases of ip protection (subsidy generation) necessarily bad if they are to produce goods that the market cannot afford to. In other words, I consider IP an effective method with which a market can conduct off-book research and development at low cost and risk. In fact, I cannot think of a better combination of incentives than the private sector taking all the risk and paying all the cost of failure, and only profiting if they succeed. This is a great set of incentives.