No it’s not. It’s safety conscious to keep space in front of you because you will need to reduce speed at a slower rate so the asshat behind you doesn’t slam into the back of you.

It’s literally safer than someone on your bumper going 80 mph (as long as you’re not in the fast lane).

That’s heavily dependent on context. Oftentimes each person commenting in these threads has a different situation in their mind.

If they’re on your ass on a multi-lane highway and there’s plenty of space for them to pass you AND you’re in the designated lane for slow traffic (eg, right-most lane in the US) then it’s not rude at all. Encourage them to get off your ass and in the meantime, you’re giving both of you more time to react in an emergency.

If you’re on a two-lane road (ie, one lane per direction) I get wanting to slow down below the speed limit, but really, you don’t know whether that person has a friend bleeding out next to them while trying to get to a hospital, or maybe they are at the boiling point for a road-rage incident with a gun in the glovebox. I maintain a safe speed and if I get to a passing zone, I make a point to slow down for them to make an easier pass.

Rude, safe, who’s to say.