What's wrong with supporting the Third Temple?

In the summer of 1990, before we made aliya, Mrs. Carl and I and the then-three children spent half a day with an organization that was creating the priestly garments and the vessels for the Temple - may it be restored speedily and in our time. The highlight of the day (for us) was when they showed us a model of the wash-basin and asked who knew how the Kohain (priest) stood when washing from