The most significant reason why using animal fur for clothes is a fashion crime is because fashion does not hurt living creatures. Killing animals in order to skin their fur is absolutely hurting living creature. Just because those animals can not communicate their feeling to human clearly, does not mean that it is not hurt to be shot, killed or hunted by human who wanted to skin them. This fashion rule seems trivial since animal never go on strike, but it must be hurt. It is not ethical to hurt other living creatures just to get everything we want.
Another reason why it is wrong to use animal fur is that it ruins the ecology balance in our nature. Our nature has its own balance, but human ruin it by destroy the food chain. Human decreases the amount of the animals which have beautiful fur too much that unexpectedly increase the amount of the other animals. Human killed too many bears, wolves, tigers and deer which make our ecology imbalanced. This imbalanced situation is not only dangerous for animals, but also human. It can cause climate change, disease, natural disaster and famine.
In general, it is wrong to use animal fur for our jackets, hats, or bags. It hurts living creature, and it destroys the ecology balance. If we are still using animal fur fr our clothes, means that we have destroyed our nature