No, you aren't wrong. I run my own league for 4 years now. My brother dropped Cam Newton (the highest scoring player) for a kicker. The team in 1st place claimed him off waivers. Unfair? yes. Really dumb? Yes. But the point is, my brother dropped him. I'm not gonna go back and change it. If this guy accepted the trade than it should have went through.
The only time I've stepped in and made in a change in 4 years was last year when my brother (the same guy) dropped his entire team because he didn't make the playoffs. I removed all his players from others people's teams because I didn't think it was right for people to do it. (Yes, I got Tom Brady and gave him up)
Fact is the guy shouldn't be using his power to help people. He should be protecting the league from retarded acts or extremely unfair trades where obvious collusion is in effect. This type of behavior just makes him look like a dick and people won't want to play in his league.
Talk to him about it, let him know you think it was unfair. If he doesn't change it back, then start your own league next year. Get your own friends and family to play. Its easy and fun.
I dropped Vick last year because Andy Reid said Kolb was starting. The next day he said Vick was actually going to start. There was nothing I could do and I didn't look for sympathy. It was my choice and I made an unfortunate one.