Economics professor: Marty' s Pizza and Checkers Pizza are the two major pizza parlors in our town  Marty' s sold coupon books including coupons good for one large plain pizza at any local pizza parlor, at Marty' s expense  But Checkers refused to accept these coupons, even though they were redeemed by all other local pizza parlors  Accepting them would have cost Checkers nothing and would have satisfied those of its potential customers who had purchased the coupon books
This shows that Checkers' s motive in refusing to accept the coupons was simply to hurt Marty' s Pizza
Any company that refuses to accept coupons issued by a competitor when doing so would satisfy some of the company's potential customers is motivated solely by the desire to hurt that competitor.