Lungi-clad men are pariahs?

On my recent visit to South Asia's largest shopping mall in Dhaka, I witnessed a very sad state of affairs. A very senior citizen, who seemed to be coming from the countryside, was stopped by the guards at the entrance of the said shopping mall because he was wearing lungi. They didn't allow him to enter the mall. When I inquired, the guard said that it was a direct order from the general manager and he might lose his job if that elderly person was caught on CCTV wearing lungi and roaming inside the mall.
My question to enterprises like these: why are they ashamed of lungi? Many people roam around wearing three quarter pants, but it doesn't bother them. And even if a foreigner enters the mall wearing shorts, they don't stop him. Then why stop our lungi-clad fellow citizens?
Syed Raiyan
Gulshan 1, Dhaka