Weapons etiquette varies greatly from place to place - what's horrible in one place is common in another.
Throwing the weapon onto the mat or giving it back to the attacker is not an issue. It's just a feature of a given line of tradition.
I one dojo you learn "you must not throw the weapon down and you have to give it back in a safe way ". (Which is what I learned.)
In another dojo you learn "you must not give back the attacking weapon for another attack. And you must not hold the weapon which is carrying the spirit of the attacker longer then needed". (I think this is mostly taught in the line of Saito sensei?)
When I practiced for the first time in a dojo of Takemusu aiki and handed back the sword to the attacker as I learned it, I nearly caused a little "turmoil".