In my limited time, I notice there are two kinds of vetoers: Those who quietly veto a trade they find suspect and then go about their business, and then those who veto trades and shout it from the rooftops, making sure everyone knows it, and demanding that everyone else veto it too.
I personally get annoyed by #2, but am totally fine with #1. You're not always gonna get 32 guys in complete agreement on every trade. Frankly, I'd be a little worried if that was the case. It's good to get opinions and make people think. I've noticed in some worlds, guys veto trades and they're up front about it, stating their reasons. It then generates CONSTRUCTIVE discussion which leads to the vetoer or trade parties seeing things differently - or at least coming closer to a common ground.
Bottom line: It's "business", so don't take it personally and be professional about it, on either side. No one is gonna be talked/ordered into vetoing a trade they don't want to veto.