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.
If someone abandons the prayer he comes out of the fold of Islam as mentioned in Fataawa: 84390 and 87319. Also, insulting the Prophets, may Allaah exalt their mention, is an act that takes a person out of the fold of Islam.
The Fiqh (Islamic jurisprudence) Encyclopedia reads: 'The scholars agreed in a consensus that a person who denies the prophecy of one of the Prophets or the Message of one of the Messengers becomes a non-Muslim. The same thing applies to him if he denies what the Prophets or the Messengers said, or insults them, or despises them, or mocks them, or makes fun of the Sunnah of the Prophet .'
Our advice is that if you hope that your friend will revert to Islam then you have to endeavour to call him to Islam, but if you are pessimistic about his re-embracing Islam, then you have to cut relations with him, and refer to Fatwa: 88293 about the limits of a relation between a Muslim and a non-Muslim. However, it is not permissible for you to curse him as it is not permissible to curse a specific person unless he dies as a non-Muslim, but it is an obligation to hate him for the sake of Allaah.
Allaah Knows best.