Please give me some tips how to advice the 50 years old Muslim man who have a new habit of buying and watching pornographic CD's with his wife and his 4 growing sons. I have tried to give some advice but he made fun of me.

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

You should advise this man in a wise manner and make clear to him the prohibition of this act that he is doing and the dangers it has on him and on his whole family. Remind him of the stories of the sinful people who did not abide by what Allah ordered them and their fate. Remind him also of the bounties that Allah has given him, like good health, peace, marriage, children and the abundant provision at a time when many people lack them.

If Allah were to take one or some of these bounties away from him, he will not live a happy life and he will not enjoy what is lawful or unlawful. So, this is a great grace from Allah to him.

If he wants to preserve these bounties, he must be grateful to Allah by obeying Him in it and avoiding to disobey Him in it; Allah Says (what means): {And [remember] when your Lord proclaimed, “If you are grateful, I will surely increase you [in favor]; but if you deny, indeed, My punishment is severe.”}[Quran 14: 7].

Allah knows best.