You are confusing the different and separate sections found within an entire eatery as being one and the same. Food prepared within those sections are done according to different culinary skills, ingredients or in the case of Muslims, "halalness".
Except for the issue of "pork" and "lard", "halal" involves saying some prayers in appreciation before the chicken or whatever animal is slaughtered. I have find it very noble in some ways.
I have no problems with this just as I, a Christian, have zero problems eating the food that has been offered to my deceased grandparents as part of my family's yearly cultural practice of ancestor worship. All I do is scoop out, if there are any, the ashes from the joss stick or burnt money/prayer paper offerings before eating the food.
Only the deranged loonies and rabid fanatics, especially those Christians who want to out-Christians established Christians, think it is a HUUUUGGGE fucking problem eating halal food, or food prepared and offered for ancestor worship.
If you want to eat, go ahead and eat it. If you don't want, then don't.
If you think an eatery is shit for converting to "halal-ism", then don't patronise it. It is as simple as that.