We, Shia Muslims believe that Muslims are Taahir (Ritually pure). Muslim corpse is Taahir depute the fact the Ghusl of Mayyit is obligatory on every Muslim dead body. Touching human corpse (before Ghusl of Mayyit) makes it obligatory on the person touched it directly with out gloves to perform Ghusl of touching the corpse.
Wassalam.