Yes, I agree that it looks like the cool natural De Niro style, but I find it funny not because it looks fake, but it's so real that it's hillarious...it really looks like De Niro wanted to kick the shit out of Batts. I just love it, as you do to.

The "natural style" is a hallmark of Martin Scorsese's technique in "Goodfellas" and also in "Mean Streets." That entire Billy Batts scene (and the one following, with Scorsese's mother) is so natural-seeming that it's hard to believe that they were working from a script.