I voted very important.
It's not critically important only because there are other many things I need to work on before I could create a situation wherein I have the option of not hurting the other person (i.e. getting out of the way). Not injuring the assailant--resolution without winners and losers--is the whole point of aikido. If you don't care about that, maybe you should quit training and go buy a handgun.
Moreover, people are pretty smart (even the wasted or insane ones to a certain degree), and might be able to read your intentions from your body language. If you mean them harm, they might pick up on that and fight harder than if you appear calm and peaceful.