I think it is local customs because Qur'an does not demand eating certain food just forbids pork, blood, animals sacrificed to other than God, animals sacrificed on stone altars and road kill, or animals killed by other animals. There is relief that if one is starving that he can eat the forbidden but only to help hunger pangs and not to overeat. Nothing about having to have to eat beef or anything.From what I've heard, most Muslims in Fiji do expect Hindus to convert and eat beef when they marry into a Muslim household. I'm not sure if that's just a local custom or part of a specific Muslim teaching though. I never looked into it.
As for the Methodist church there, while it's not part of the official church doctrine for Hindus converting to Christian to eat beef, there is a certain amount of pressure placed on them to do so.
A while back, one of my nephews converted to Christian from Hindu and now attends a local Methodist church in Fiji. He and nearly half the congregation are Indian and live in Hindu households where eating beef is strictly forbidden. Despite this, or perhaps because of it, the church leaders organized a luncheon where beef was served. No one was forced to eat it mind you, but when several people refused, it was strongly implied that if they wanted to be Christian they had to give up all Hindu ways. That's what actually prompted me to start this thread over 6 months ago. It just struck me as being incredibly insensitive.