The biggest reason the ivory trade is a problem is that it is illegal. Not only is selling ivory wrong because of killing an innocent animal it is also an illegal process. If you are caught smuggling ivory to other countries around the world you will most likely spend a while in a prison and probably be fined.
What the people who want to stop the trade are most upset about is that in order to get ivory you must kill a wild, innocent and endangered elephant. Ivory is not a naturally occurring substance