It’s not always a choice whether to consume it though is it? There are huge swathes of the population who have no interest in politics, but every time they turn the tv on or see the papers in the supermarket they hear people talk about ‘boris’ like he’s one of the lads and see people saying Jeremy Corbyn is anti Semitic. It adds up.
Talk to anyone who’s not political about Jeremy Corbyn and they’ll all say exactly the same things. The things that the media want them to say.
Nailed it imo, it's the people who are not that politically engaged who it effects the most. I have friends who pay no attention to politics whatsoever other than when election time comes around. I wouldn't class any of them as consumers of right wing media but if you mention Corbyn to them they will bring up the usual right wing media talking points such as 'Isn't he 'Anti Semitic ?', "Doesn't he sympathise with Terrorists ?', 'Won't he bankrupt the country ?'... They don't necessarily believe the claims as they are distrustful of the media but it's a sign of how casual consumption of the media can influence how you perceive someone.
Look at the Mail Online, it pulls in something like 15 million different visitors every day, millions of them will not be interested in politics and will just be there for the celebrity articles, sport etc but all that time they are on the site they are probably being exposed to the daily negative headlines about Corybn even if they don't read the articles.
Whether Corbyn deserves the negative headlines is another topic altogether and not really relevant, the fact is the media has and always will influence how portions of the public vote. Propaganda exists because it works.