So far the only offensive term you've been able to come up with that does not violate your general idea is "bad" - i.e., a pure, non-descriptive value judgment. In short, what you have argued - interpreting your somewhat ambiguous statement in the light of your examples - is that value judgment terms are okay only so long as they carry not a shred of description. Once they gain a descriptive dimension, then they are ruled out. What you wrote is somewhat ambiguous but your example supports this interpretation. The only acceptable word is "bad". You resist ruling out "anemic" but your own criterion forces you to rule it out.

And here's the problem: non-descriptive words are not very offensive, because to offend someone you need to explain what it is about them that is the cause of your low opinion of them. "I have a low opinion of you" just doesn't cut it.

The word "anemic" actually begins to offer a description of the badness, if a metaphorical one. This supports the value judgment by explaining what it is about the target that deserves the value judgment. But the problem is - it's descriptive. And so it classifies. Because any description classifies.