Proportional r. is good because anarchy is impossible

First past the post elections tend to result in a two-party system because people respond to the actions of other people. People will end up voting only for those parties which they know have a realistic chance of success. The problem with fptp is that we end up with a two-party system. This is obviously bad because our own choice is restricted and so too is that of other people. Given that (due to Duverger's law) a two-party system will emerge from fptp it makes no sense to vote for parties which endorse this system. It is bad to live in a country with fptp so it is logical for voters to support parties which endorse pr. To vote for fptp is illogical.