In my experience (and this is explicitly anecdotal) ... it seems like liberal memes tend to either satirize a politician's actions or repeat opinion-based editorial info, while conservative memes are more often explicitly fake ... yes, satirical/op-ed memes obviously exist there, but I see more obviously false and easily-debunked conservative memes.

For the conservative, those op-ed memes can tend to be interpreted as the oft-quoted "fake news", which is where I'm guessing the "both sides" sentiment comes from.

Again, that's just entirely my anecdotal experience.