I blame The Belstone Fox.
Obviously banning foxhunting doesn't do much for foxes. If we really wanted to do something useful to alleviate the suffering of foxes and other wild animals we would cut the speed limit on the roads.
It is important symbolically though. We don't mind too much if foxes are killed under cover of darkness by traps, stony-faced pest controllers or careless drivers because it seems an inevitable part of modern life, and nobody is rubbing our faces in it so we don't have to think about much it anyway. Hunting on the other hand looks too much like a celebration of cruelty. (And we have the X-Factor for that nowadays.)
I think we are fairly uncomfortable with our relationships with animals. One the one hand we keep them as pets, anthropomorphise them relentlessly, and generally would like to treat the fluffier ones as we treat our own children if we could. On the other hand we eat them, keep them in cages, wear their skins, experiment on them, feed them to each other, and kill the less useful ones to protect the more useful. It is almost impossible to come to a consistent moral viewpoint on animal welfare. I am sure that it is our own moral discomfort arising from this inconsistency that fuels much of the anger towards hunting, which is in essence a very ostentatious and rather nostalgic display of that subjugation of animals which makes our lives what they are. If hunting stops altogether, it won't stop us inflicting enormous amounts of suffering on animals for our own convenience, but at least we won't have to suffer the indignity of being reminded of it by poshos in red coats galloping about and blowing their tiny trumpets.