Just to be clear - what opined claim of mine are you saying you have disproved here? I see assertions, but no disproof of any specific claim.
I also noticed that you haven't backed up your claim (that memes are should be counted as created works, and therefore subject to copyright laws) with facts or evidence, either. "You can look that up" isn't providing evidence.
But let's just say, for the sake of argument, that memes are created works, and that copyright laws should apply to them (I'm not granting that in reality, but just for the sake of argument).
Your point is that passing off someone else's work as your own is plagiarism.
When someone submits a meme, that person does not make a statement one way or the other about whether that work is their own or not. Therefore, in the normal course of things, someone reposting another person's meme would not be liable for any kind of plagiarism at all, since they have made no specific statement of authorship (even granting the hypothetical idea that memes are created works subject to copyright laws).
That's why there can be nothing unethical, even theoretically, about reposting a meme: the person reposting it isn't making a claim of authorship.
Here's an example of one such reposted meme, so you can see what I mean about not making a claim of authorship, if you have time. If you read the comments you'll notice that there is a comment that makes a statement about plagiarism, and the original meme is linked in the thread also.
Here is the link:
imgflip.com/i/r8tcs
I also want to reiterate that this is all hypothetical, anyway. I don't believe that copyright law is appropriate to bring up for this discussion. I don't believe memes are intended to be an individual's own created work. That may not sway you, and that's fine, but that's where I stand on it until I'm given a reason to believe otherwise. You yourself said it wouldn't be actionable.