Yep! Jack is a few fries short of a Happy meal. There is a saying in medicine "First do no harm." He want to stop Sayid from kicking Uncle Henry's butt and, in the same breath said he's willing to take the chance with everyone elses lives by letting the clock run out.
Hey let's form an Army but, you shouldn't hurt anyone. At least not anyone on the Other's team. He's loosing it big time. He's out of his element and feeling the pressure.

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Hope is a very dangerous thing to lose. - Sayid

I do what my Rice Krispies tell me to. - Anonymous