Yes, political doctrines and ideologies are the subject of political sciences. It applies to both historical and contemporary ones.
Feminism is an ideology that makes claims about the social reality, which can be analysed and prooved, exactly in the same way as the claims made by libertarianism or communism. Of course, any questions about what's just or good, requires to give the definition of justice or wellness to judge against. It's the only way to answer them in objective way.
Some questions may be better fit on History, Philosophy or Cognitive Sciences, but political sciences are interdisciplinary per definition. It doesn't make them off-topic here, but just makes more likely to become an answer on that other site.