There is NO excuse for striking a student in the face, especially a new student. It doesn't serve the purpose of teaching and shows no respect for the person by the instructor. If one applies the misguided notion that this is a martial art and therefore we should accept whatever abuse an instructor dishes out under the guise of teaching than we are missing the whole point of our training, to improve ourselves.
This type treatment is demeaning and not in the spirit of Aikido. It teaches only distrust and will erode respect for the instructor, not cultivate it.
Anyone who trains hard will experience some form of physical damage at some point, minor or severe, it just comes with the territory.
Sometimes Sensei will dress you down or even get a little rough to help you improve.
Let's not confuse this with an ego trip by an instructor who thinks they can slap people around to make a point (by the way, try that approach at your job tomorrow and see how long it takes to get arrested).
Not a softie but let's get real here. If that happened to me I'd be out the door before the word comply left the bullies mouth.