It's possible to make leather out of the skin of any animal, you know. (Fact fans might be interested to know that the best quality leather comes, perhaps surprisingly, from ostriches.)
So, if we were to send the pelts of fifty lovely little freshly-skinned chinchillas to a tanner rather than a furrier prior to selling the result to Madonna, she would end up with a hideously expensive jacket that would not only arouse zero outrage but would also look considerably less shite than the one she did, in fact, buy.
I have heard the argument that the reason fur is more reprehensible than leather is that leather comes from animals that are killed for meat, whereas fur is from animals that are killed for their fur, their meat being discarded as a waste product. Firstly, this strikes me as somewhat selectively and stupidly squeamish. Either you come to terms with the idea of killing animals or you don't. What's so noble about killing them for food rather than clothing? It's not like we humans live in the tooth and claw of the wild and would die if we didn't eat meat; vegetarian diets are perfectly nutritious, even if you don't like the flavour. Eating meat is every bit as much a selfish choice made to satisfy your own personal taste as is wearing fur. You, personally, may be at ease with killing for food but not for clothing, and that's fine, but I hardly think that that position is so morally unassailable that you can justify screams of outrage from the mob at anyone who feels differently.
Secondly, where's all the outrage directed at vegetarians who wear leather? For them, it's not a waste product. It puzzles me, actually, that so many vegetarians who won't touch gelatine or rennet — waste products both — are content to wear leather shoes.
People forget what the original reason for the anti-fur campaigns of the Twentieth Century was. Fur often came from endangered species. Some tribesman would trek into the Amazon, kill one of four rare jungle cats left in existence, sell the pelt for, oh, 50p, and it would eventually be sold to some ugly woman with a cigarette holder for a million squillion gajillion pounds. This, for a whole raft of reasons that I shouldn't need to explain, was a problem. A problem completely and utterly solved by fur-farming. Chinchillas, in fact, are a pretty good example: they were hunted into endangerment back in the days when fur came from the wild; now, they're farmed, and not so endangered. Great.
Of course, there are plenty of good arguments to be made against fur-farming on anti-cruelty grounds. Not a single one of those arguments applies to fur without also applying to meat, leather, and milk.
Let's be honest here. Madonna has been singled out for attack for two reasons. One: chinchillas are cute. Two: meat tastes good.