They're ignorant cowards
Seriously, this looks like an awfully fair trade. One the one side you have Haren and Ethier. Haren's considered a good SP1 (ADP ~50), though he's injured and has a history of fading. Ethier may break out, though he's modestly priced in drafts (goes in the 120-160 range). Ichiro's the biggest "star" of the group, with an ADP in the 30's. He's an elite source of speed and avg, which could make all the difference to a team that needs to make up for some deficiences in the lineup. Without looking at the teams, I can easily see this being a trade that helps both sides. And that's where the veto probably comes from. You're either playing with idiots, or unethical cowards (who don't want to see those two teams improve themselves, but would be all for something like a James Loney for Albert Pujols trade in their favor).