Against the Association Fallacy

Much as I noted that the appeal to consequences fallacy comes up often in atheist/theist discourse (see my related post in 2013, "Against the Appeal to Consequences"), the association fallacy has as well. The very claim "atheism killed millions in the 20th century" (generally citing the Soviet Union and Maoist China) or "religion caused the crusades" (insert whatever examples in here that apply) is the association fallacy.

The Marxists responsible for these communist atrocities were indeed atheists, and the Crusades were obviously religious wars (although other factors also had a part). Yet all atheists, or people who have a religion, are hardly responsible for them. It could be argued these were a necessary result of these ideas, so even if individuals are not responsible, these ideas are.

However this too does not seem plausible. Is an atheist who's an Objectivist (a philosophy completely opposed to Marxism) responsible for the atrocities of Marxists? A religious pacifist for those of Crusaders or jihadists? To ever claim this requires painting everyone with the same brush. One must show why atheism or religion causes such misdeeds, regardless of details. To my knowledge this cannot be done. 

Claims of this kind are not only gross overgeneralizations, but a grave injustice for any person who does not share dogmatic, violence-affirming ideologies. On a practical level, these aspersions can do no more than alienate people, as they rightly find it deeply offensive, and discredit the people who make them through doing so in their minds, no matter what valid points may be offered on other topics. It's enough already, I'd say.