I doubt that Geary's slur had much to do with the Corleone biological family. Geary was referring primarily to Mafia business practices, i.e. perpetrating all manner of skullduggery, under the thinly-veiled pretense of respectability.

Regardless, it's clear that Geary had way overplayed his hand with that remark, that the insult had hurt Michael's considerable pride - and that Michael permitted himself a rare moment of personal pique in response to it. Pacino played that scene with a brilliant, instinctive sense of understatement, conveying Michael's latent cockiness in the way he subtly bobbed his head while seated in his executive chair, as he began his "Senator, you can have my answer now if you like..." reply.

The very first time I ever watched that scene, I recall thinking: 'Geary, you have no idea who you're dealing with. You think you do. But you're about to find out for real'.

I believe Michael had correctly sized up Geary as a bit of a hayseed: Greedy and corrupt for sure, and eager to exploit his position as a US Senator - from Nevada no less. But naive, unsophisticated, and way out of his league to think he could ever successfully shake down a Mafia don - especially one as ruthless as Michael Corleone.

~ Q