He is being asked to denounce evil by e-mail

Firstly: the basic principle is that denunciation of evil is a fard kafaayah (communal obligation), so if sufficient people undertake it, the rest are absolved of sin. 

Al-Nawawi (may Allaah have mercy on him) said in his commentary on Saheeh Muslim: 

Enjoining what is good and forbidding what is evil is fard kafaayah (communal obligation); if some people do it then the rest are absolved of sin, but if no one  does it, everyone who was able to do it with no excuse or fear (but did not do it) is guilty of sin. But it may also be an individual obligation, such as if a person is in a situation where no one else knows of it but him, or no one can remove it but him, or such as if a man sees his wife, child or slave committing an evil action or failing to do something good. End quote. 

But we must not forget the obligation of enjoining what is good and forbidding what is evil. The Muslims should do that, because the Prophet (peace and blessings of Allaah be upon him) said: “Whoever among you sees an evil action, let him change it with his hand (by taking action); if he cannot then with his tongue (by speaking out); and if he cannot then with his heart (by hating it and feeling that it is wrong), and that is the weakest of faith.” Narrated by Muslim, 49. 

This becomes more important the worse the evil action is, and there is no evil action worse than insulting Allaah and His religion Islam, or insulting His Messenger Muhammad (peace and blessings of Allaah be upon him). 

Whoever comes across any of these evil actions, in a newspaper or magazine, or on a satellite channel or elsewhere has to denounce it as much as he can, with his hand (by taking action), with his tongue (by speaking out) or with his heart (by hating it), as enjoined by the Prophet (peace and blessings of Allaah be upon him). 

Whoever does not see it or come across it, but is told of it by others, should also hasten to denounce it, by getting in touch with the newspaper or channel, or getting in touch with the writer of the article himself, and denouncing them. If people see how many are denouncing it they will be deterred from repeating the evil action, and they may even apologize publicly and repent. 

Moreover, if many people agree on denouncing an evil action, that will be indicative of the power of the religious people, and their protective jealousy and their awareness of what is being broadcast and published. This is something that is required by sharee’ah, otherwise you will find that every day someone dares to say something bad about Islam. 

Moreover, this is a means of earning reward, for the one who denounces evil will be rewarded. 

We ask Allaah to make our religion prevail and to humiliate the people of deviance and misguidance. And Allaah knows best.