The novel backs you up, Whisper. I believe it says that Michael contrasted his calm with Enzo's shaking hands. It wasn't macho posturing on Michael's part--it was his growing self-realization that he needed to stand by his family at their time of need. It also subtly reinforced Michael's "icy calm" nature in the face of danger and other stresses that would cloud other people's minds with emotion and harm their judgment.