What is the ruling on working for a man who owns an internet cafe that contains indecent websites?

If the work involves operating these sites or contributing to them, then it is not permissible, because it is assisting in sin, according to the Almighty’s saying: "And do not cooperate in sin and aggression." However, if the work is not related to these sites, then there is no objection to working, while advising the employer to abandon this evil.