They all profess to lean one way or another politically and hence each is chosen by an individual of a similar leaning to bolster his or her beliefs. Feed them what they want to read and they'll believe it
This is the crux of the matter, Drone. I would like to pick upon this point and add some.
People buy political orientated papers to "bolster" their outlooks, as you rightly say. Hence the newspaper, rather than a beacon of objectivity, becomes an endorsement for an individuals social, political, economic viewpoint and convictions.
This is nothing new of course, but in this mega-globalised world, with so many cultures and social stratafications mixing together, there is a segment of society that needs their views demonstrated and represented.
They have tended to be your typical Daily Mail reader (I think), but are increasingly your left leaning person as well. The left need their views reinforced, and why wouldn't they?
Anyhow, here's a basic question....
Did The Daily Mail make that person hate Muslims, or did they hate Muslims already???
Did Donald Trump divide America, or actually did he simply reflect that America is already divided???
Speaking hypothetically, did that porno, Hollywood movie or Eminem song make me sick, or was I already sick?
To summarise, if politics is indeed an art form, we need to accept that Politian's like Trump and Farage are reflecting a public want and desire.
They do give oxygen to sensationalism, and hence journalistically everything reported about them is journalistically sensationalist too, but they are NOT exclusively responsible for every 'nut job' who does an act of madness, (if you get my drift).
They represent and reflect the anger, but they are not the root or cause of it...