Only Labour benefit from first past the post

The problem with the first past the post system of voting is that it tends to reduce the amount of viable parties to just two. The reason for this is that voters react to how they expect the rest of the electorate to vote and they end up supporting candidates which are already popular. But this is bad for freedom and it is bad for democracy. Democracy tends to reduce the size of the state (if it doesn't it serves no purpose) and so then if the choice is reduced to just two parties this will be detrimental to freedom.

Liberals on the right tend to prefer freedom and they like democracy but this means that a centre-right party which opposes democracy (and supports first past the post) will be unappealing to liberals who would naturally support such a centre-right party. First past the post makes both of the main parties unappealing to liberals because they support democracy and then by definition oppose fptp. Because liberals will generally reject a party which supports fptp and because (as a rule) both parties in a fptp system support fptp... liberals will be more disenfranchised by fptp than the left. It is the left who do better with fptp because liberals who would tend to be on the right are repulsed by the two-party system and so those votes are lost meaning that the left take power. First past the post is helpful to the left because liberals will reject (both) fptp parties meaning that only non-liberals remain. First past the post is bad for liberalism which means it makes no sense for anyone but a socialist to support it. In a first past the post duopoly there is only one party which truly benefits from the lack of choice and it is the party of the left. There is no benefit to the right to be derived from first past the post... not even for the party of the centre-right (such as the Tories) because their support for fptp will drive liberal voters away... only Labour benefit from first past the post.