First past the post is illegitimate

If we seek to form a government we have an obligation to make sure we have a mandate from the people we seek to govern. Usually this is achieved by democracy and arranging elections... but if those elections are not proportional we have not given the people the best chance to reject bad politicians. If we seek to form a government we have an obligation to make sure not only that there is democracy but also that there is proportional democracy. If we have not used a proportional voting system then the government has no legitimacy. Only if we use some form of pr can we make the claim that the government is legitimate. If we use fptp to form a government then that government has no legitimacy.