I have tended to think this way. It even seems obvious that God is not bound by petty notions of doctrine and right practice. He must be above all that. But I've become wary of "obvious" things. So then it also occurs to me that there are other possibilities too. For example the idea that God must be good is culturally specific. The ancient gods were not good, they were capricious and looked out for themselves. Another possibility is that God is good in a sense that we cannot understand. There are perhaps yet more possibilities we can't even imagine.
I like the Kingdom of Heaven quote. But it makes me suspicious because I like it. It somehow forces God to be a liberal, enlightened version of a deity made in man's image. Isn't that a bit too convenient? What if God is so completely other that we cannot describe in terms of personality, goodness, or even action? When we presume to say anything positively about God we presume a lot.