I'm on the fence with this one, since it's a competitor and you're researching products, advertisers DO pay a ton of money to get the word out on all their products and a $0.25 click is probably a drop in the bucket of a serious ad budget.
The only people that would get screwed in this situation are affiliates that use AdWords to promote products and gain nothing from that "research" click whatsoever. At this point you have to take sides and determine which bottom you're going to defend :)
The silliest part of all is:
WHY IN THE HECK WOULD YOU CLICK ADS ON YOUR COMPETITORS SITE AND GIVE THEM MONEY!
Not the sharpest tacks on the corkboard for sure.