i dislike Kabuto, but you're waaaaaaaay off. He doesn't seem concerned in the slightest at being outnumbered by two uchiha. Still, it's better for him to have those two fight it out than to fight both of them himself, even an idiot can see that.
This^^^ if you've watched Kabuto fight before you would see how he usually tries the easier route, than a full on brawl (he stated that). But he's willing to fight regardless if he needs it, he was playing it smart.he's not begging for mercy. Why fight both of them if he might be able to get them to fight each other? It's called psychological warfare. Look it up. He's clearly not adverse to fighting both of them, he seems down for it.