Since you don't seem to be arguing, I would like to understand what you mean? Did I use such a pejorative? I'd sincerely like to know - if, that is, your query is sincere as well.
I'm just musing, and hoping someone might have an explanation. Language is complicated, and emotionally-loaded words are especially so.
Let me put it this way. If I call someone cancerous, I'm not trivializing the group of people that have cancer and distilling them to a pejorative. In general, if I use a disease as an insult it's fine, but if I use a disability as an insult it's usually offensive. They're both afflictions, but they're treated differently in uncountable ways.
I could list some reasons, but none of them really feel like they get at the root cause of the difference. Do you have any insight?
Perhaps it's related to self-identification? People don't self-identify as cancerous, the cancer (or disease?) is an external actor invading the body. Whereas a disability is a feature or aspect of one's body.
(I don't have first hand experience with either, so I'm just musing too..)
