Originally posted by FrothByteI was thinking about that too, though I just figured he'd do it remotely like you said if he could.
Well the Destroyer seems like magical tech. So that makes it quite different.In any case, we don't know how the mind gem works either, same way we don't know how those sentinels morph and imitate powers. Right now all I have going is the assumption that an infinity gem is more powerful than some kind of techno-mutant hybrid.
But if you really want to contest whether Ultron can hack them or not, I'd recommend concentrating on how Ultron can actually gain access to their file systems. They're not connected to the internet as far as I know. So either Ultron needs to find what wavelength/frequency they communicate with (if they even communicate) or he'll have to physically tap into them. Hacking can't be done through thin air.
Still, your right. It's possible I'm overthinking the sentinels and the "all magic is just tech we don't understand" statements.