Here we go. Stuf about Israel that you posted will be in italics.
Israel had a cutting tongue, made fun of abuse victims, and was prone to rage. John is the same, but he has no issues swearing up a storm. He also makes fun of everyone, no matter who they are.
However he had a warm heart underneath it all, that's part of the reason that Yasumi fell for him. This one not so much, but it is there. Why else would he agree, however annoyed he might be, to train Shea and Earl? He wouldn't have if he didn't have a warm heart... Somewhere under the twisted mess that he is.
Israel's attitude was partially a defense mechanism that he had set up earlier in his life. No differences here. John simply can't turn it off.
The only way to fight bullies was to stand up to them with words and fists, even if he lost. This, and his father.
That was basically what John was, a bully who takes his rage from home out on people that he thinks are weak. That was why he was so obsessed with strength, because to be without it was the equivalent to castration to him. He takes his rage out on everyone. Except for his few friends. And if he's ever without strength he'll work and gain more. Because he hates the weakness in himself.
The only way to fight his kind was to be stronger than him, and Israel was good at that. This is why Israel pursued strength. Again, no comment here. The only way to beat the strong was to become stronger himself.
But strength wasn't enough, the strong rule the weak, and the smart rule the strong. Israel became stronger by becoming smarter and being a good chess player. That was the secret to Israel's strength. Wow, this one is nuts! John views intelligence as strength. Sure, beating the foe through power alone is good, but what about foes that are just as tough as you? You have to be smarter than them. That's how John beat Israel last time. Because he played Israel's emotions like a fiddle. I'm betting that next time, that won't happen.
No matter what Israel's opponent throws at him he overcomes it with a strategy. Insert John where it says Israel. Seriously. The two of them build from their loss and turn it around on the other. That's why they'll go back and forth so much. That's why they will always win one then lose one.
Do you get my point now? The two of them are a lot alike, but neither one wants to admit it.
Edit: Most of John's insults are wise cracking. He's just not as subtle about it. :P