How we cite our quotes: All quotations are from A Man for All Seasons.
Quote #4
MORE: […] I will not give in, because I oppose it. Not my pride, not my spleen, nor any other of my appetites, but "I" do, "I." Is there in the midst of all this muscle, no single sinew that serves no appetite of Norfolk's, but is just Norfolk? There is! Give that some exercise, my lord!
DUKE: Thomas!
MORE: ... because, as you stand, you'll go before your Maker ill-conditioned!
More is accusing his friend of being spineless, more or less. That may be the case—or it may be that Norfolk's religion simply isn't very institutional and he just assumes the new church will be as good as the old one. At any rate, it's unclear to More where Norfolk's "self" really lies and whether it is founded on any unmovable principles. Is Norfolk willing to be absolute about anything?
Quote #5
MARGARET: Father. "God more regards the thoughts of the heart than the words of the mouth." Well, so you've always told me.
MORE: Yes.
MARGARET: Then say the words of the oath, and in your heart think otherwise.
MORE: What is an oath then, but words we say to God? Listen, Meg. When a man takes an oath, he's holding his own self in his own hands like water. And if he opens his fingers then, he needn't hope to find himself again. Some men aren't capable of this, but I'd be loathed to think your father one of them.
Margaret might make a good case—but she's also being a bit of a sophist, twisting good logic to bad ends (as far as More is concerned). She's saying that More's inner self and outer words and actions are two different realms: He can believe one thing and say another. But for More, this division isn't a good thing—he thinks it's his moral duty to make his outward actions consistent with his inner self.
Quote #6
MARGARET: If you elect to suffer for it, you elect to be a hero.
MORE: That's very neat. But look now. If we lived in a state where virtue was profitable, common sense would make us saintly. But since we see that avarice, anger, pride and stupidity, commonly profit far beyond charity, modesty, justice and thought... perhaps we must stand fast a little... even at the risk of being heroes.
Margaret also tries to talk More into signing the oath by claiming he's making himself a hero by not doing it—potentially stoking his vanity. But for More, he's not trying to be a hero—it's merely incidental to the fact that he needs to follow these principles. The point is to be true to himself, and he's not attached to how society views him afterwards, hero or no.