I understand this physician's rationale behind dumping in too much fluid simply because it's possible with a larger bore catheter - BUT - if you still have access to rope like veins prior to cardiovascular collapse in a big trauma patient, I, your OR friend, will GREATLY appreciate that big access. You have to think past the first 15 minutes of a trauma case - that patient will in all likelihood end up in an OR. Early vascular access is a HUGE help, and can save some precious time.
No offense to your NYC trauma buddies, but I can promise you that if that trauma patient comes to my OR with a couple of 18's because the damn ER doc thought that was big enough, we will have a chat post-op - and I will be putting in an 8FR introducer in the IJ so I will have plenty of access. And having to take the time to put in bigger access when it could have been done earlier is really gonna irritate me.
Butterfly needles are for drawing blood - nothing more, ever - end of discussion.