If two groups have a disagreement, the one who arrived there second should leave. If they were there at the same time, the smaller one should leave. If they are of equal sizes (or in a disagreement between single people, not in groups) the one with the problem should leave, amirite?

Number or people who agree with either group are counted as part of that group when size is the deciding factor.

If it's at a party, the one that the host dislikes leaves, although he/she/they shouldn't be there in the first place, unless there with a friend of the host.

It's all circumstantial really.