When a member of kennedy's cabinet expressed concern over the plan to invade cuba, the attorney general (and kennedy's brother) pulled the dissenter aside and told him to support kennedy's decision. in this case, the attorney general was acting as a

Group think

Explanation:

Group think occurs when well-educated high posted well-intention-ed people make an irrational and wrong decision which is not good at all. The members of the group also support that decision making it rational. In a group think the other member have to refrain from expressing their doubts, decisions, judgment, and disagreement with the decision. It is the ignorance of ethical law and its moral consequences.  

To minimize this error of thinking provide full time to discuss the topic and allow group members to share their viewpoints.