and there is a fence there...

It's turf and dollars on the part of the senior folks, it's what the British call 'cap badge' loyalty for most -- simple unit loyalty and the unfortunate human tendency to make ones self feel better by trashing others (even if partly in jest).

It is counterproductive and my sensing is that it's less a problem now than it used to be. Still around and needs to get better As more elements from both sides of that fence work together, it will.