Jouez avec le bon handicapIf you are a weak player, your stronger opponent will thank you for taking the correct handicap. Many people find it extremely boring to be in a game with a foregone conclusion. Playing stronger players is a good way to improve but you will have trouble finding willing opponents if you do not offer them an interesting game. For example, a top European player, has his own specific way of refusing any underhandicap games, he says "it spoils his style" -- rather an effective way of implying the suggestion for the handicap is not entirely what he wants, and some others are sure to have developed methods of their own.
If you are a strong player, you may consider playing weaker players as a service to the game and to IGS. Furthermore, playing a weaker player with proper handicap should be just as challenging as playing an even game against a player of the same rank. Also, just consider how important playing those stronger was to your advancing to your current rank; how would it be without those? -- it goes both ways.
Continue to "first stone".