Any process in which a virus stops, prevents, or reduces the frequency, rate or extent of host tapasin (TAP binding protein/TAPBP) activity. Tapasin is a type I transmembrane protein essential for the optimal expression of stable MHC class I molecules on the host cell surface. By inhibiting host tapasin activity, viruses can prevent presentation of their antigens at the cell surface, and thereby evade the host anti-viral immune response.