Most of them are pretty unfamiliar with summoners relationship to the spirits so they probably thought "oh that guy slashed the spirit its gonna come back right?" Or "oh he just killed a spirit guess she'll have to get another one"
we clearly have someone who knew that losing a spirit is like losing a child, what's he doing not educating people.?!?!???
Well thats cuz most people in that story don't really care for summoners cuz I think they are generally weaker than wizards (summoner can only usually use 1 element or anything similar to that element while wizards can use a variety is what they said) so pretty much the guy dint bother educating they would just brush it off.
And yes they should probably educate that but realistically people wouldn't give a shit if a summoners spirit died since it doesn't concern them or relate to that. Maybe parents can understand. But idk my thoughts.
T H E FU CK WAS THAT!!! nobody cared that he kill undine, like whats wrong with these people??!?!?!?!?!?!?!?!?