First past the post is authoritarian

With a proportional voting system voters are able to put much more 'information' into the system. They are better able to express what they like and don't like. They are better able to expose the government (and as a consequence everyone) to the reality of their opinions. With fptp reality is delayed because the two-party system makes it easy for the state to ignore its voters. With pr the state must be much more responsive to the people. Since reality is inherently libertarian and people want to be left alone more than they want to be protected more democracy will lead to more freedom. First past the post suppresses freedom because it enables the state to assume authority where it is not wanted. Proportional representation makes it easier for the people to reject the government. Coercion and authoritarianism are bad so if people are better able to reject these things this is good. A lack of democracy makes bad things easier (and freedom less likely).