Earlier on in this debate I argued that Marxism is a religion
I would like to hear why you think that it is not a religion
I got a bit of spare time, so here is it goes.
In general, Atheists will attack Marxism as a "religion", "faith", "dogma" or call it an "ideology" with the inference it is false and dogmatic. They do so principally to dissociate themselves from Marxism and, basically, treat it as "not real atheism". The "Marxism is a Religion" accusation is usually never thought out in any depth or with an effort to prove it. The "truth" of the accusation is simply self-evident to most of it's accusers and no debate or evidence is required.
Now, I don't think there is any doubt that Marxism as a movement has behaved like a religion. The obsessions over theory and Marxist writings as "scripture", the endless division in to factions, the Personality Cults, the mausoleums for the dead leaders, the kids waving little red books, destroying temples, statues, etc. All of this certainly is very similar to religion. Though I have never been religious, my own experience suggests that the inner psychology of Marxism is also very similar to a religion.
But these are generally defined by the nature of social groups, how people form and act on beliefs and sources of authority in determining what people believe and do. They are not unique to religion or to cults, but exist in very secular surroundings (if to a much lesser degree). Scientists can disagree amongst themselves. We attach an exaggerated importance to celebrities and public figures in a way very similar to personality cults. The way people follow Richard Dawkins and Sam Harris as celebrity atheists borders on the cult-like at times. Music festivals play on the same use of crowd psychology that a political rally or even a church service does. And Football hooligans, bonded by their favourite team, can be extremely destructive by rioting and destroying property when their team loses. Fox hunting is very secular, but is really a form of ritualised killing as "sport" and the violence and aggression of Boxing is another socially acceptable and managed form of ritualised and destructive behaviour. It's not unique to religion or to "ideologies" as some would put it, though it may be on the bigger scale because of the power dynamics and importance of the consequences involved.
I'm going to side step the question of "is Marxism a science" and "is Marxism true", but what defines religion is not a specific set of social behaviours, institution or psychology, but is rather the belief in god and the belief in the supernatural. This Marxism does not subscribe to and thus it cannot be considered a religion. This would hold true even if Communists have admittedly repeatedly behaved like religious fanatics and fundamentalists.