Dr. Stockmann: "A party is like a sausage machine; it mashes up all sorts of heads together into the same mincemeat--fatheads and blockheads, all in one mash!" (5.76)
The Doctor seems to have no respect for any political party at all by this point in the play. To him, any large group that unites to form ideas is inevitably full of lies. The only real truths are to be found with individuals.