While there is little doubt that taking a special interest in a particular area can allow the person to make better decisions within that area, this is not a reason to accept that person's judgment.
When someone blindly accepts an expert's opinion over their own, they give up their individuality and make themselves slaves to another's will. All people have their own agendas, their own biases, their own vested interests, and also make mistakes.
Saying 'it must be true because renowned expert X said so' is not so very different from quoting the Bible or Koran at someone and insisting it makes you right.
On the other hand, saying 'I believe it is true because expert X said so, and he has been right about a lot of other things, and doesn't seem to have any vested interest in this regard' is a much more powerful and rational judgment.
And 'I believe it is true because expert X said so, and expert X is highly regarded by person Y whom I trust' is a weaker, but still reasonable judgment.
But making a judgment because a person you know almost nothing about (except that you have been told that he is highly regarded by others that you know almost nothing about) said it was true, is one of the weakest and most abused arguments which one can make.
The recommendations of nearly every government committee are based on this kind of argument. They are nearly worthless.
See