It's a slap, being told he is the one making his brother unhappy. Even more so when Aria is the one spitting it on his face. It's enough for Eli to want to shred him to pieces. But then Aria goes on.

"Incestuos?" He is up on a jolt, which only has him wincing as once again the world becomes unstabble around him. That doesn't stop him though. Holding onto the edge of the bed to keep his balance, Eli slowly steps off it. "Don't bring Sybil and the cubs into this! And take that shite back!"