The evidence is based on what was given. If the parent cannot convince the team/management then there is something wrong.

It could be confidence.

It could be social standing.

It could be that they are not explaining their viewpoint properly to the stake holders.

If the parent is not gaining traction and blaming it on intelligence, likely, the parent can't see others viewpoints either and is not trying to bring the team along...

Engineering is not just systems...

It's not my job an as engineer to fight a broken decision-making process. If the manager sees that he repeatedly makes wrong decisions, then it's his responsibility to answer why, not mine. I'm him subordinate, not the other way around.