He's mad that Sasuke might have cheated and caused this miserable situation for both Sakura and Sarada. Before, it was just a kid having insecurities. Now, it's a serious thing that Sasuke did.
Naruto seemed very pissed in regards to Sasuke´s actions, not in regards of Karin per se.
I´m hyped to know how is this drama going to unfold... are Sasucakes and Narucakes gonna fight?
Will Sarada come to her senses? (yes, she has the right to be mad. No she shouldn´t hate -hate is such a strong word- Sakura; at one point the kid has to admit that "liar" has done more for her than her two biological parents combined).