Style Over Substance

Unfortunately the style with which an argument is presented is sometimes taken as adding to the substance or strength of the argument.

Example:

You've just been told by the salesperson that the new Maytag is an excellent washing machine because it has a double washing cycle. If you were to notice that the salesperson smiled at you and was well dressed, this wouldn't add to the quality of the original argument, but unfortunately it does for those who are influenced by style over substance, as most of us are.