My dad always says, "What makes America great is the fact anybody can sue anybody else, at any time, for any reason...whether they collect or not is another issue." So, you may be "in the right" but if you get sued, you still have to
prove to a jury that you were right (and spend $$,$$$ to lawyer up for this privilege, I mean, opportunity to exercise your rights).
So, with regards to memes, just to be clear...in the US, you *do NOT* have the
right to make meme's..."fair use" is allowed, BUT, this is an affirmative
defense !
Just like my daddy said, you can make something, post it online, and still get dragged to court...where you then (if you want to say "It was fair use!") say, yes I did it, but it falls under "fair use." And then, the jury gets to decide (after lawyers on both sides ring up an appropriate amount of billable hours).
FYI, here are the standard jury instructions that the US 9th Circuit uses, to give the jury the necessary background info to decide if what you (the defendant) did actually was "fair use."
http://www3.ce9.uscourts.gov/jury-instructions/node/280