Go blame very early taxonomy.
With that said they did have some foreseight, we did get the word raptor after all (which is more related to birds despite being used on certain dinosaurs).
Also smug science absolutism is pretty much just casuals or plebs thinking they know science when the very essence of science is fact-checking and changing established stuff because of new facts.
IIRC, the word Raptor wasn't used because of any similarity to birds. Its Latin meaning was intended, "plunderer" or something along those lines, because of the idea that these animals were egg stealers. Just a coincidence that they turned out to be (the forerunners of) birds.
This and the Pluto deplanetization are guaranteed flashpoints on the internet.
The Pluto thing isn't like this, though. It's not denial of reality. What we call Pluto is subjective, so if someone disagrees, that's just their opinion. It's not a "fact" that Pluto is or isn't a planet, it's a designation. No actual facts about Pluto are in significant dispute. No one's saying it's not real, or is actually bigger, or anything. So while I think people should get over it, it's not a big deal.
This dinosaur thing is different. It is reality denial. It's no different than saying the Earth doesn't orbit the sun.