The Tories are to the left of the people

First past the post is good if the voters are to the left of the Tories... then fptp prevents them getting the socialism they want because (fearing Labour) they will vote for the Tories and not get as much socialism as otherwise. Ignoring the fact that if they are to the left of the Tories they might vote Labour. (We can assume Labour are too extreme even for a left-wing electorate.) Fptp is good only if the Tories are right wing. If the Tories are to the left of the population then proportional representation is preferable.