Originally Posted by Loss Leader
I think you have that backwards. It is FPTP that delivers straight majorities to one party - even when that party gets well below a majority of the vote. It promotes gerrymandering since it is so easy to manipulate boundaries. It also forces a 2 party system on the population since a vote for anybody else is a vote that is "thrown away".
It is only under MMP or multiple member electorates with PR that candidates from smaller parties have a chance to be elected so you can sure that there will be "a multiplicity of parties representing all sorts of political demographics" come election time.