Social media has taught us a lot about ourselves—including things we'd probably rather not know. For example, some people seem to love "chicken scissor salad."
Joining the ranks of linguistic missteps like the substitution of "colon" for "cologne" or "Super Bowel" for "Super Bowl," the "scissor salad"/"Caesar salad" confusion is somehow way funnier and far more mind-boggling. And, as with so much online, it's often unclear if people are fooling around when they type it.
Undoubtedly, some people are in on the joke and simply perpetuating it.
What we do know for sure is that Googling "scissor salad" gives us the results for "Caesar salad," so it's a common enough mistake that it's accounted for in search algorithms. That's not great news, but it may be better than some alternatives...
Again, no need to fear for the future of the written word: a lot of these people are just goofing. And both malapropisms are easily explained—one could use scissors to cut up the salad ingredients, or shake them up in a bowl as if having a seizure. Sure, restaurateur Caesar Cardini is said to have invented the dish in the 1920s, but that was a hundred years ago. The future belongs to scissors and seizures!