God is the ultimate being, perfect in every respect, completely self-sufficient. How can such a being be made "finite" by a mere description? I have no argument with Christ that God is good, that is absolutely true. The question is whether or not that is so because God is confined by the description and meets its parameters, or whether the word itself finds its definition in what it is describing. Good is good, in other words, insofar as it describes God.
The consideration is not mere semantical puffery, the Bible gives me some leeway to explore such a claim. Jesus said that God is unknowable apart from self-disclosure. And he also said that God is uniquely good. It seems to me, then, that God is also the only one who knows what is good, and does so on the basis of his self-knowledge.
Good, by this reckoning, is whatever God is, and whatever God is, is good. I think we waste time arguing with the uninformed that God is only good, when they cite what they consider is evil behavior (like the slaughter of the Canaanites). They don't know what good is and therefore are clueless as to what evil is. God is the measure of good, and by extension, anything that which is not aligned with God is not good: evil, simply, is the un-God.