I agree, projectivism strongly predicts that emotional faculties will be vital to moral development. But most cognitivist approaches would also predict that the emotional brain has a large role to play. For example, consider this part of the article:

Damage to VM cortex results in difficulties in attributing emotional states to others on the basis of facial and vocal characteristics (Shamay-Tsoory et al., 2003), and leads to the disruption of the subjective experience of emotion, as indicated by self-report (Bechara et al., 2000, Damasio et al. 1990). What we can conclude from these studies is that VM patients have emotional deficits, and have difficulty in attributing emotions to others, and thus that they may not be reliable in emotion attribution.

People who can't tell whether others are suffering or prospering are going to be seriously impaired in moral learning, on almost any philosophical ethical view.