  The thought is that when an outcome is democratically chosen and some people disagree with the outcome, as some inevitably will, they still have a duty to go along with the decision because otherwise they would be treating the others unfairly. If they refuse to go along and disrupt the democratically chosen arrangements, they are assuming for themselves a right to determine how things should go that overrides the equal rights of all the others. They are, in Peter Singer's words, assuming the positions of dictators in relation to the others. For if they turned out to be in the majority, they would demand the compliance of the others.