You don't have to. That's actually a place where automation could help. You could just use image detection and auto-tag stuff as to what you think it contains. Then, have a list of sensitive tags that are automatically blurred out in the feed (and let users customize the list as they see fit).

If it's something trending towards illegal, toss it into an "emergency" queue for moderators to hand-verify and don't make it visible until it's been checked.

So in your example, if someone uploads war imagery, it would be tagged as "war," "violence," "gore" and be auto-blurred for users. That doesn't mean the post or account needs to be outright nuked, just treated differently from SFW stuff.