They should definitely not let kids fight or there would be more violence. Some people just do messed up things because they can't cope with their problems correctly, it's the way of the world. Shit happens.
I'm sorry but back before this whole mindset of "our kids are precious and can do no wrong" people sorted their problems out (physically or verbally) and went about their business. When your techer or parent would tell you to go outside and settle it.
Now, everyone gets their feelings hurt so quickly they resort to shooting teachers, other students and themselves because of bullies or emotional bullshit.
I'm not saying that there weren't emotional things in the past, but nothing like school shootings once or twice a year...