Don't bring down your best owner to everyone else's level. Bring them up to his. If you really want to make your league more competitive, educate your other owners by explaining basic principles.
For example, something every owner should understand when evaluating a trade proposal - BENCH PLAYERS DON'T SCORE FANTASY POINTS:
How many players am I receiving that I will start each week, and how many points will those starters get me?
How many starting players am I giving up, and how many points will they (or are they) getting me?
Generally speaking, those need to be nearly even for you to consider the trade. As I always say to my owners, you can offer me all the hundreds of players in the Arena and Canadian football leagues for my kicker, and there is no way I agree to that trade. Or, put in a more practical way, give me Julius Jones, Brandon Jackson, Lendale White, and Ladell Betts for the injury-prone Westbrook - sure I am getting a lot of bodies, but I can only start ONE of them, costing me a ton of fantasy points each week.
Just explain basic principles like this to the other owners so they know how to evaluate trades. Then this guy will be unable to take advantage of them.
(Of course, any time you're trading bench players or upside players, especially early in the season, it is every man's determination of what value to place on that. But a good rule of thumb is simply, how many points am I getting and how many points am I giving up. Guys on your bench don't score you points.)