It is just Halloween. No one complains when a kid wears a firefighter or police costume, even when it is cheaply made and cheezy. Doctors and Nurses don't complain when people go as Doctors or nurses. Why should we be so thin skinned that we can't handle people wearing kilts.
People who dress up at Halloween do it for fun and escape. It is not an affront to anyone in most cases.
I would rather spend money on another kilt than have to waste money on a costume I will wear only once. I'm going kilted, I'm going comfortable, I'm not making fun of Kilted folk.