David, you're just mincing words.
The (Latin) prefix "non-" means "not". i.e. the reverse of, other than, absence of. Therefore, Non-violent is equivalent to Not violent.
All MA training environments are by their nature contrived and ritualistic facsimiles of varied violent scenarios - whether such contrived action/response/counter-response are "controlled" or not. The only action I would deem truly not-violent is one in which uke is greeted and embraced with open arms - kisses are of course optional.
Although I accept your commendable, if somewhat idealistic, premise of a not-violent (non-violent?) Aikido, this thread is about atemi/striking, and by it's nature is diametrically opposed to any precept of non-violence (or not-violence?).
By its very definition, any action involving a "strike" is violent, whether that strike is controlled or indiscriminate, and whether it is delivered within the context of a contrived scenario or a seemingly random and unpredictable state of confusion. To me it's really a question of degree.