First past the post is bad if tactical voting is real

If there is no difference between the electorate and the government then fptp and pr are similar. But if there is a significant difference between the two then pr is preferable because excess government is tyranny if it does not have a democratic mandate. Only democratic force is justified and if pr would reduce the size of government then pr is good. Pr might not reduce the size of government but it would never increase it. If people do not vote tactically under fptp and would vote the same way with pr then (of course) fptp makes no difference but if people do vote tactically then pr is preferable. There is nothing to fear in pr if there is no tactical voting under fptp and if there is then pr is preferable because excess government is tyranny. Fptp is a problem unless tactical voting doesn't exist.