That was very insensitive of that employee to treat you like that. She probably thought she was doing the right thing but it was rude and uncalled for. The coupons may have saved you some money on a next purchase but if you are like me I would not have used them, I may have given them away though. When people are rude to me I do not go back to that store., they have lost my business.
I'm the same way. I know it probably isn't hurting their bottom line reallly. But if I quit going, and every other customer treated like crap stopped going, and all of their friends and family... eventually, its going to add up.