This is a dumb comment. The AC is not threatening to physically harm anyone in any way, or proposing any kind of punishment for climate deniers to be performed by humans. He's only saying that he'll be happy to see them "hoist by their own petard". There's nothing wrong with feeling satisfaction after watching someone suffer due to their own stupidity and bad decisions, especially when their actions are in fact harmful to the rest of society.
Honestly, at this point, there's nothing we can do to stop massive climate change because of the deplorables and their mouthpieces like Breitbart. We're not going to change their minds; people like this fundamentally do not believe in science. So the next best thing is to just wait for the apocalypse to happen, and then take satisfaction in watching these morons suffer due to it.