Media effects are a controversial topic, hotly debated in academic circles and widely (mis-)applied by pressure groups from both left- and right-wing positions.
Conservative, right-wing politicos, media and campaigners love to lash out at sex and violence in film, music, games and TV, often essentially applying the near-century-old hypodermic syringe model which argued there's a direct link between media content and the views, attitudes and behaviour of those exposed to them.
Despite being the topic of many, many 1000s of academic studies, there still has been no definitive evidence for this. If it were true, why doesn't every Michael Bay filmic violence fest produce millions of new psychopaths roaming the streets? Why hasn't the best-selling Grand Theft Auto series lead to millions of crazed drivers mowing down pedestrians?
There's also the problem of selectively ignoring news content seen as favourable to conservative, right-wing views: graphic (so-called; it's an ideologically loaded term) coverage of terrorist atrocities (with ideological judgements on the scale of importance of lives based on skin and geography), glorifying coverage of military ventures, supposed 'smart' bombs and all.
The left can be just as censorious, seeking restrictions on free speech where this might undermine minorities or the less powerful groups in society. An overlap can be seen with attacks on sexual content as exploiting women and creating negative social attitudes.
On the press, the left, including the commentator linked below, take a more structural approach: the political economy branch of media academic theory.
This focuses on ownership and industry structures including distribution (and concentration of ownership). Chomsky's propaganda model is a classic example.
The article below produces a decent piece of evidence to back argument made, that UK public opinion on political parties and leaders is shaped by press coverage under the direction of non-resident billionaire owners bitterly opposed to any left-wing policies, especially crackdown on tax avoidance, that threaten their comfortable existence and corporate interests.