Were the Cathars Christian?

Analyse: major differences between their ideas and orthodox catholic teachings of that time (12-13 centuries), consider the Albigensian crusade against them, analyse wether their ideas were essentially different from Christian beliefs (any fundamental differences that may tell us that they created a new religion? If yes, what constitutes it? What made these heretics different from Muslims then?), their use of Bible, etc. State the point of view (for example, they were Cristians or they were not Christians or they were somewhere between, etc). Make a conclusion. Issues/problems in analysing the topic, may be some contra arguments.