Appeal to the majority
An appeal to the majority (also called argumentum ad populum)is the logical fallacy of believing that because something is popular, it is right.For example, using the argument that most Americans support the death penalty as an argument for the death penalty is an appeal to the majority and does not logically support the argument.
A more common case in general use is the unspoken assumption that because a majority of a group approves of an action all group members approve of that action.
For example, if one person commits robbery against another person this is judged morally wrong by most people. In contrast, if the majority subset of a large group of people decide to commit robbery against another person in the group to distribute amongst themselves, this is considered by some to be morally correct Democracy and welfare, leading to the fear of the Tyranny of the Majority.
The appeal to the majority is a modification of the logical fallacy appeal to authority, in that greater numbers are thought to give greater authority to a position or action.
Three experts instead of one doesn't make an assumption more right and three people instead of one don't have more authority over a fourth person than any of the three acting individually have.