Why did you lose ply?

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.

Its true that there are no universal preferences, but ability is about as universal as you can get. The deaf community doesn't prefer deafness to hearing, they just like having a community. If they genuinely preferred deafness to hearing they'd advocate destroying their hearing infants' eardrums... but in fact they find that idea abhorrent. The existence of transabled has nothing to do with preferences, only with identity. The only major groups that prefer disability to ability are the practitioners of female genital mutilation... and their attitudes toward sexuality are pretty disordered.

I certainly agree that its important to avoid treating the disabled as having lower value as people but I don't see how calling situations lame makes me devalue lame people and see them as a disability rather than as a person. I also don't know what that has to do with sidewalk ramps. Surely that has more to do with efficient resourse allocation vs a desire to increase inclusivity... I don't think the proper balance is obvious at all.

Now I certainly agree its important to value disabled people just like abled

I'm mostly working by accepting what amounts to received wisdom from bloggers, who say that "idiot" and "moron" (and for that matter "retarded") are not okay. I don't desperately want any of these words, and the above alternatives exist without (as far as I can tell) offending the bloggers or the people they speak for, so I invest a minor effort in the vocab shift. I'm less willing to do this sort of thing when there is no viable alternative word with the right features.

I use "crazy" and "insane" sometimes, but I have been encouraging the preexisting shift in their meanings towards a not-necessarily-negative meaning of "extreme" (e.g. "this ice cream is insanely yummy!")

to figure out where 'loony' came from, but I've never seen it considered offensive so I suspect you're okay.

Loony? As in "loony bin"? How could that possibly be considered less offensive than 'lame'? It is a huge deprecation of those with mental health problems. Of course mental health problems are lower status than physical ones - and for something to be 'offensive' the insulted group has to have social power.