Intellectual property exists as a concept to foster the creation of more intellectual property. That is not the case for all private property, because I cannot copy your land or your car infinitely. That’s why IP rights expire at some point, or have fair use that doesn’t harm the IP rights holder, something other forms of property don’t have. Saying that they are equivalent is not foolish—I think that’s a bit extreme—but it doesn’t recognize that they have fundamental differences, and the laws around them have different intended outcomes.
I think AI training falls most likely in the fair use category of intellectual property: there is some societal benefit* that requires no actual harm** to the IP holder, therefore it’s a good trade-off for society if we poke a hole in the social construct of property to get that benefit.
*Let’s put aside the question of whether AI is good for society or private ownership of AI models is good for society. Important questions but separate from the theory. IF IT IS GOOD, it follows the above. If it is not good, then of course it does not.
**Also not a fully settled question. Again, an important debate to have and the tradeoffs here matter. If the harms are small enough, the societal benefit could be worth it. Both notes have to be true for this to be worthy of “fair use”.