No two people are exactly the same, but we group them together in various ways. The question to ask is "for a particular purpose, should they be treated with the same reasoning?".
For the purpose of creating new art from experiencing previously created art, why should we treat them differently?
The purpose of the copyright law is to reward authors through property rights for their work to protect them against theft and incentivizes them to be able to earn a living from their work too. That does not happen if someone can take the work, feed it as extra data to a statistics machine and earn money from their work without their permission.
If AI training should be fair use has nothing to do about how it works (search engines fall under fair use regardless of if they think or not) but the effects it have on the original author.
So when people talk about humans and AIs "doing the same thing", AIs are not legal entities like humans are to begin with, the entire premise is moot.
For the purpose of creating new art from experiencing previously created art, why should we treat them differently?