That's classic rock heresy.
I agree with him on Def Leppard particularly because they only ever play the most over rated rock anthem Pour Some Sugar On Me. I have never heard radio play anything else.
While on Def Leppard I dislike anything they did after Adrenalize. Became too commercialised for my liking.
Black Sabbath did some pretty dire stuff too but You Won't Change Me was annoying for me because of the organ. Not keen at all on that song. Not to mention a fair chunk of Never Say Die was average. That is an album I still hope will grow on me somehow.
The only Led Zeppelin song I would say I do dislike is Your Time Is Gonna Come for the same reason I dislike that Sabbath song, I don't like organs dominating a song. Not a fan of that sound.