Proportional representation is an obligation

The state has an obligation to use proportional representation in its elections otherwise there will be the problem of a two-party system. The intention of democracy is to enable the people to reject and refuse government intervention. If there is not sufficient (proportional) democracy then the voters will be subject to the least unpopular of the two main parties and will not easily be able to reject the government. If we are truly represented then we can reject the government but with fptp it is hard to reject the government because we can only choose the least bad of two parties (if we want to be sure that our vote will count). There is no legitimate reason for the state to use anything other than proportional representation. There is no legitimate reason for the state to stifle democracy.