There are champs people REALLY want to play
There are champs people want to play
There are champs people don't mind playing
There are champs people don't want to play, but they will suck it up and go through with it.
Then there are champs people REALLY don't want to play.
People dodging because they didn't get a strong contender, their main, or just got some average champion are petty.
Dodging because you keep getting champions you don't want to play consecutively is alright or if you don't mind playing a certain champ, but not in the mood for them at that moment of time is alright.
It is not a hardcore mode, but you still want to be motivated and have fun while you do it.
I personally go through with a champion if I get them, and I accept people's trades no matter what, but if somebody doesn't want to suffer because they get a champion they really don't want to play at that moment of time, let them dodge.
Players being forced to utilize that champion regardless if they dodge will deter people from Aram, and I can imagine people holding off from playing it for days purely because of that, depending on how stubborn they are.