I've been thinking about this a bit further. Honestly, it's probably a balance that swings back and forth. If people were only copying memes without thinking, then it would be good to remind them there's no law against trying something fresh every now and then, because that's good too.
But on imgflip right now, we're too much the other way. Someone likes a joke and retells it, and you have 20 little assclowns climbing over each other to see who can say "Repost!" first (even if it's already written in the comments numerous times.) That's when it's time to remind people of the basics of Memes 101 - that memes are, in fact, mostly made of derivative elements and not original creative works, and that it is in fact okay to repost memes (as long as it's within site guidelines).
Basically people should be free to make whatever memes they want. If they want to do original ones, that's great. Some of those come out OK. If they want to repost one, that's fine too. Personally I usually find those the funniest.
In other words, I'm not really against people making original memes, I'm against people imposing artificial standards on others that make no sense (e.g., memes should "only" be original). So that's kind of the background to what I was thinking in my comment.