What if take-aways had to display on the door "All our meat products are halal" ? Or if supermarkets had to keep all the halal 'food' in one location, clearly labelled ? Then you'd have a clear, informed choice, and that is, after all, what has been taken away.
I believe that Denmark has recently banned all ritual slaughter (both halal and kosher) on animal welfare grounds, and that New Zealand are close to doing the same.
Maybe that's the way forward? Get the anti's and the tree-huggers on the case !