As Mike told Tom: "You're not a wartime Consiglieri, Tom. Things may get rough with the move we're trying."

As the quote above points out, neither Vito or Mike were under any illusions. They wanted Moe's casino (which, by the way, they owned part of) one way or the other. Mike didn't mince words. He was going to get the casino one way or the other. So, his words to Moe were straightforward.

As far as Moe and Barzini go, sure Moe knew what the Corleones intentions were and he was looking for allies. Why not Barzini?

"Generosity. That was my first mistake."
"Experience must be our only guide; reason may mislead us."
"Instagram is Twitter for people who can't read."