I would like to think a pilot wouldn't just ignore an instruction, but at the very least query it.
I the case mentioned, I agree with Single Spey that ultimately the pilot is responsible for the safety of his/her aircraft. However be prepared to back up you reasons when the subsequent forms are filed.
There is usally a very good reason why an ATCo will send you around aircraft which may not just include other a i.e the vehicle that has been seen passing the hold.... the deer spotted about to leg it across the runway
