sem613: There’s a big difference between a preference and a demand. In your case, you wouldn’t want it. You may even ask to switch. But what if the response was “No”? Would you then refuse to sit in your seat? That is the issue here. I have no problem with someone requesting a seat change. But you can’t demand it, then refuse to sit in the sit you were assigned if you don’t get your way.
Let them learn the Igros Moshe a bit, where R’ Moshe zt”l paskens that it’s muttar l’chatchilah to sit next to a woman on a bus or train. I see no reason the same shouldn’t apply here.