Hum to be honest i really think this is a gross mixup of intelligence and capacity to adapt socially. Somebody very intelligent can communicate at very different levels without having to adapt. I see lots of very clever people doing this without even realizing it. That's because engaging someone vary much more on other criterias than on the mere intelligence of your interlocutor, like social context, aim of the conversation, etc ..<p>So the pejorative connotation of condescension fits in this context, the context of people thinking they have to adapt because their interlocutor is dumber than they are, when in fact it is they that lacks the social intelligence that would make adaptation natural.