No, he has a very valid point.
His point is the polar opposite of valid.
This was not even borrowed power
Well, technically it was. Like I said, Obito giving his chakra to Kakashi by inhabiting him is very similar to Hagaromo giving his chakra to Naruto and Sasuke, which subsequently lead to them awakening the Six Paths Senjutsu and Rinnegan respectively. Either way, the "borrowed power" argument is stupid as hell for the reasons I stated above.
, as we literally saw Obito's spirit rise up from the cow fodder remains and posses his body.
Doesn't change anything really. Obito's chakra/spirit enabled Kakashi to use the Double MS. But since it was Kakashi himself who made use of the powers he was blessed with, it's a form by which we can judge his power.
It was not his power, not even by a long shot. You cannot even call it his power, as it was Obito's power channeling through him.
Again, I don't give a rats ass about the "not his own power" statement. That argument is not going to work with me, since everyone inherited chakra from the Shinju. Under the OP's logic, Juubi jins should not be included in power lists, since sealing the Juubi inside of them gives them the ability to use the Onmyoudon balls, enhanced durability, flight and greater speed. Is that "not there own power"? Same goes for Naruto and Sasuke inheriting Hagaromo's chakra like I stated above. The entire borrowed power argument and anything even closely related to it literally needs to be burrowed 6 feet under the ground.
Alright, you wanna be a fanboy. Im done.
-Has no valid counter
-Calls the opposition a "fanboy"
Where on god's green earth have I seen this before? Rather platitudinous I must say.