Re: if he asks you to...
Islam says "Amr bil maruf wa nahi anil munker" enjoy good deeds and stop from doing wrong". So Islam is no body's personal matter and a muslim is not free to do wat he wants. .
there's a hadees if u see someone doing wrong stop from ur hand(by force) if u can't do that stop by tongue. if even that's not possible then think it bad in ur heart and move on and this is the weakest Iman.