This is one of the things that disturb me most when thinking about aikidō.
And other than historical, philosophical or techniqual question I don't have any clue how to ever get answer:
Why do people who deeply believe in pacifism practice a budō?
Why do people who do not want to hurt or injure another human being practice a martial art?
Why don't they learn one of the methods or ways that use and teach pacifistic ways to deal with aggressors or conflicts? There is so much to be learned if someone wants to. And it is really not an easy way to go. I myself think, it's much more chalenging than doing aikidō.
I'll add a question. What makes anyone think that a technique done on someone intent on doing you harm, who hasn't learned ukemi, will leave them unharmed?