It's not avant-garde, the expression in this form for what I know was coined by the 19th century German philosopher Max Stirner.

The nub of the issue though is not really if something is theft on a legal definitional level. Laws themselves are extremely rarely enacted by direct decisions of those who are commanded to follow them. so they don't reflect what the vast majority of people would consider moral, which often include reciprocity, fairness, and staying beneficial to the society as a whole rather than benefit a tiny minority with highly detrimental consequences for the rest of people.

Copyright protects random individuals in the same way it protects corporations.