All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
You have to advise him in a good manner and soft words as the right of the husband is great on his wife. Even if the husband commits some sins, his right on you is still outstanding. For your advice to have a desirable and beneficial effect on him, you have to choose the appropriate and suitable time to advise him. You should not ask for divorce for this reason. We advise you to fulfil his rights on you and do not show any signs of anger and discontent whenever he sits with you, because showing these signs make things even worse and this does not solve the problem. However, you can offer him a book about the seriousness of backbiting and slandering and holding other people in contempt. You can also provide him with a beneficial and influential lecture on tape. For instance you may make use of Riyaadh As-Saaliheen written by Imaam An-Nawawi and there are many books in bookshops which address backbiting and its effects.
Allaah knows best.