Ah yeah that one bugs me too.

The one that has been really annoying me lately is when someone refers to a group of people that ends in "-ist", and it's a group so you obviously use the plural, but they don't put an "s" at the end for some reason. Something like "Antifa and BLM are just a bunch of terrorist!" or, "The Communist are trying to take over the country." or "They call us a bunch of right wing extremist, but I don't see what is so extreme about upholding the Constitution." I see it all the freaking time, and I truly don't get it. My best guess is because people leave off the "s" when they say it out loud, and it sounds fine to them, they end up spelling it that way too.