If you frame their pushback as kingdom building and spite vs. lack of exposure and experience, you'll be filled with anxiety
"in contrast to interpretations of their own behavior, people tend to (unduly) emphasize the agent's internal characteristics (character or intention), rather than external factors, in explaining other people's behavior."
"THAT PM thinks they can design, what a tool!"
We can all be better at this.
One challenge here is you feel you "shouldn't have to" show this! It is an unfair burden of proof!
Helpful exercise...consider how you've changed perspectives personally. Was it be told? Or being shown?
Sales "PdM is all high and mighty"
PdM "Sales doesn't understand"
Design "Eng and PdM don't understand"
Eng "PdM doesn't understand"
IT "yawn, next"
Support "oh dear"
The challenge is here to stay. On some level, we all need to embrace it.