Sadly, needs must!
However, when saying goodbye at the cockpit door, if anyone is wearing anything Man U related, I always tell them they are "lucky I didn't see that before takeoff, or you wouldn't have come!" Have even been at the gate and pointed out someone wearing a United top, and said loudly, "That fella over there with that red top on needs to change his shirt if he wants to get on. I'm a Man City fan and I won't allow it!" Usually gets a laugh, but have seen a concerned face or two!
I think I already told this one, but I met Gordon Brown and his bodyguard in SFO and when I mentioned City, he told his son, Alistair, to turn around...City sweatshirt! Good lad!
;-)