You notably don't say which subreddit. [edit: the point being that some Reddit subs are favored by "lefties" while some are favored by people with other ideological outlooks. I would add another point: the mods may well have looked at your other comments to help guide their decision. Finally, we don't know the actual language of your comment ... the sort of comment you have described is often stated in a way violates norms]
> Thou shalt not post anything that might cause a lefty to question their opinions.
This is hyperbole at best. [edit: to be extremely charitable]
Edit: BTW, your worldview of who the good guys and bad guys are seems to be the opposite of the OP's, who is saying that the mods are ok with footage of IDF winning battles but not ok with footage of them losing battles, which does not sound characteristic of "leftys", nor does the name of the sub: /r/CombatFootage doesn't exactly sound like a "leftys" hangout. Further, the OP makes a point of stating that he wasn't mocking the IDF for losing the battle and yet was banned, which seems to clearly indicate that he thinks the mods are fans of the IDF ... again, that doesn't sound like "leftys". So by your own lights it seems that it's not leftys who reject anything that might cause their opinions to be questioned, at least not in this instance.