As a pedantic point, the majority of people supported some sort of action against Iraq. They may like to "remember" otherwise, but like Vietnam it started off with good support.
Would it really have made it more "moral" if there had been a UN mandate ? Don't see it myself, but I've never seen how murdering people in vast numbers can fit within law, even when necessary.
As for the relative ethics of those who rescued him and Mr. Kember himself, they are quite independant.
The recuers did what they believed was the right thing in spite of him being a pain in their arse. That fits the "Good Samaritan" defintion of a moral act, which as you may recall labours the fact that it is your duty to be good to people you don't like as well as those you do.
Same applies to Mr. Kember. He genuinely feels he can help. I personally think he stands absolutely no chance of making a difference of any kind, but he is at least trying, and to fight against stupidly high odds with little chance of success strikes me as quite noble.
He has been less than gracious in thanking his captors, and thus finds himself in the position of the politicos he despises. To get things done, you have to work with people you see as bad. You can keep your hands clean, but at the price of simply being a distant ineffectual voice, like the hordes who wandered streets protesting against the war then went back to their nice warm safe homes.