I've seen it play out a few times. Trolls crawl away pretty quickly once they realize their hand-crafted, artisanal insults against other memers are destined to be nuked.
Despite what you may have heard from self-professed "free speech absolutists," harassment/trolling is against ImgFlip TOS. The Global MODs don't always do a great job containing it, but Stream MODs should feel empowered to do so regardless.
And we often hear that the targets of harassment should "just deal with it." It's good advice, of course, but it doesn't negate the troll's share of blame, and not everyone is able to do that. There is a real person behind every screen-name (Russian bots excepted), and we don't know their life situation.
Roll safe and just be a nice person when interacting with others online. It's not that hard to do. We all learned how to communicate respectfully from our mothers, or we should have.