Hmmmm....in an ideal world, reasoning and communication would be the best answer, but this isn't an ideal world. For some, a smack down is the only way to reinforce the lesson of unacceptable behaviour and it's consequences. Violence is the only communication some people know.
A prime example of this is a man making unwanted psyichal sexual advances on a woman i.e. grabbing her breasts, touching her buttocks etc. If the women has made it quite clear verbally she isn't interested, and her friends have made it quite clear verbally also (a warning per se). If the man continues in this unacceptable behaviour, whilst not ideal, it is quite accetable socially at least for a male friend of said women (or the woman herself, if she is able) to "Punish" said man psyichally. I'd dare say he deserved it, but ideal, no.