The manner in which an argument (or arguer) is presented is taken to affect the likelihood that the conclusion is true.
While it is true that the manner in which an argument is presented will affect whether people believe that its conclusion is true, nonetheless, the truth of the conclusion does not depend on the manner in which the argument is presented.
Nixon lost the presidential debate because of the sweat on his forehead.
Trudeau knows how to move a crowd. He must be right.
Why don't you take the advice of that nicely dressed young man?
In order to show that this fallacy is being committed, show that the style in this case does not affect the truth or falsity of the conclusion.