Teams require teamwork. If someone on the team is an expert in a certain area, then they should be trusted to handle that area even if another teammate disagrees. Teammates who know just enough about another role to be dangerous can sometimes hinder teamwork through second guessing. I have seen too many people question the judgement of experts to the detriment of the team because they thought they knew enough to have a valid opinion. Deferring to the expert makes me a great teammate because it demonstrates trust and allows me to focus on making decisions in my own area.