Another behavior that will never count against the player

So, I queue up for ARAM, get in the pre game lobby and get a champion I don't really feel like playing. I offer a trade for a champ I would very much like to play. The guy refuses, then trades with somebody else. Cool. But then I reroll and this asshole then takes the champ I rerolled from the discarded champion pool and then proceeds to play it. Now it makes sense to refuse a trade if you don't want the champ offered or want the one you have, but to refuse when you want to play the one offered and don't need the one you have is just dicking somebody over for no reason. This shithead though is either never getting punished or if he does this won't be listed in the reasons why was.