because people speak English
just give them a sign
try to show him the right way when you eat with him but in suggestive way and be carefull when u do this
I think that what we say will be offensive for them even though we say it in a polite way. That's why, if we eat politely, this will be a kind of lesson and the person eventually will change the way he/she eats.
Tell Separately to him tha Muhmmed(SAAW)said:"Name the God,and eat by your right hand and eat from your side"
it could be crazy,
do u tried to ask politely? :p
then...don't tell him,just mention the talk.