Good point Jun. I'm more of the opinion that the atemi in such a situation needs to be committed and a real threat to the attacker, because otherwise I don't think you're going to get your attacker to respond the way you want.
Regarding the level of force or strength of the atemi, I think it would depend on the specific facts and circumstances, such as: the size of the attacker and defender, physical surroundings (indoor/outdoor, large/small area), speed of the attacker, skill level of the defender, and awareness/preparedness of the defender, among other things. I remember I read a post by Rocky Izumi Sensei, who quoted Akira Tohei Sensei, saying:
"On the mats, or outside, one should try and achieve harmony. In the dojo, we hope there are no crazies so we should not act crazy. Outside is another matter. There are many crazies out there and we should harmonize with them also. In the street, use street technique. If the person is a little crazy, you should also be a little crazy."
-from Kjartan Clausen's http://www.aikidofaq.com
So, does that then qualify as "crazy love?"