The PIC was responsible for keeping himself and all his passengers alive no matter what curve balls ATC threw at him.
An option of last resort would have been for him to climb to 6500 and proceed as planned. Let ATC sort the mess out. Better to be alive and answering to panel of armchair experts the next day than not. This is an option that should not be abused but should always be in the back of any PICs mind. We are not there to make ATC’s life “easier”, rather it’s their rather highly paid job to sort our mess out.