A department or a school is judged as a whole. I often hear canards about one part of a unit by members of other parts. You may not appreciate others' methods and sources, but outsiders do, and those outsiders matter. Research grants flow to most and those grants are competitive. The big fact about the modern American university is that the faculty allies itself with those at other universities in their field or area. It is those external judgments that play a big role in tenure and evaluation.
I am not saying that the canards do not have a basis in fact. But let them be made by others than within your unit. And you don't have to be a cheerleader for all. But you can be a cheerleader for what you do value, and silent about the rest. This is not about loyalty, rather it is about how the world views your unit.
It makes sense to help your colleagues do stronger work, just because that will help you and your colleagues look better. Strength is indicated by generosity.