First past the post duopolies are left wing

The problem with fptp is that honest non-tactical votes often allow the establishment parties to get in. This might not be too much of a problem if the two establishment parties are equal but opposite... (if the left-right dichotomy holds up) but in reality there is a difference between left and right which is often missed: The right-wing party in a fptp duopoly is a defensive reaction to the nature of majoritarian elections. Typically liberals and libertarians would choose disparate individual small parties to vote for. The emergence of a singular 'establishment' party is a result of fptp psephology.

This may then lead to even more collectivism on the left and a similar monolithic political party will form in opposition.

Freedom results from the negation of tyranny... good things happen when crime and mischief is removed... we get freedom not from the presence of the centre-right party but from the absence of the centre-left party which means the left-right paradigm which emerges under fptp is not benign. It would be better to have a plethora of small parties which each could get representation.