I would say to go for it, Frank hasn't met any Geth, but dislikes them for reasons that will be revealed later. It adds to the character development. He's just being friendly to the Krogan because he knows how well they fight, and would rather not be on the receiving end of his rifle.
Edit: Interesting tidbit, this Roleplay has urged me to go back to playing the ME3 multiplayer again. I'm a bit rusty, but am glad to see it hasn't become any less fun for me.