I'm not certain what "the R word" is, but if you mean "retard" (and derivatives), then there's absolutely nothing wrong with that word. No reasonable person is offended by calling things retarded.

I agree that no person should be offended. Obviously that's not ground truth..

If we could all agree that life would be easier if people were offended less, then instead of only trying to get people to offend other people less by telling them what is acceptable to say we could also get people to try to not take offense as much when they hear what they don't want to hear we'd have solved the offense problem from both ends.

TL;DR: Just be nice. Life's easier when you're nice even when people aren't nice to you but it does take effort.