Patton also had a kind of mutual admiration society with the leading German generals. They were both in the forefront of military thought at the time. He respected their innovations and they saw him as a fellow innovator and a skilled commander. Patton didn't have the same experience with the Soviets. There wasn't the kind of clear two-way understanding there, and Patton and the Soviet commanders may not have had much knowledge of or admiration for each other.
Patton understood what Soviet society was all about, but he may have seriously underestimated Soviet military capabilities. And he didn't exactly have his fingers on the pulse of the American public and didn't have much of an idea of what Americans wanted at the end of the war.
Of course, I don’t know if the scene in the movie really happened the way it did. But I could see Patton doing what he did with the Russian General: refusing to drink a toast with the Russian general, but respecting the Russian general, after he called him a “Sukin Syn” in return, and agreeing to do through with the toast.