The appeal to loyalty is a logical fallacy committed when the premise of an argument uses a perceived need for loyalty of some sort to distract from the issue being discussed.
Example
B questions A's statement of x. Anyone who questions A is disloyal. Therefore, B is wrong. Problem: Even if B is disloyal, that doesn't mean that B is wrong, as A is not necessarily always right.
See also Groupthink Blood is thicker than water
References