Sounds like this is more of a debate about semantics. "Whataboutism" is a recently-popularized term that doesn't have a concrete definition yet. You see it as a tool to escape a debate by diverting attention, but I see it as a tool to highlight hypocrisy while continuing a debate. Really, I guess what matters is context - specifically, whether one is attempting to debate "in good faith" (another recently-popularized, inconsistently-defined term).
I certainly don't know you or your personal relationship with your dad. He doesn't sound like a great debate opponent, but to be fair, neither do you. Most people aren't nowadays, sad to say. Somewhere between Trump and Biden, people forgot how to wait their turn and debate the idea, rather than the person. It takes two to tango, they say, and it's becoming increasingly difficult to find two individuals who are able to set aside their egos and listen in earnest to opposing beliefs.
I guess I'm a bit biased. 2020 turned me into a misanthrope. š¤·