It's not really "news" that changes people's minds though, it's memes. I'm not being an autist here, this is an important distinction. There are lots of examples of true facts that people just ignore. And lots of things that aren't news but sound good so people believe it.
Dawkins coined the term "meme" to mean that the idea was self-propagating like a virus. Sometimes news is a meme, but not always.
What spreads isn't news, nor is it truth. What spreads is a particular kind of idea that somehow imbeds itself in a person's brain for some strange reason having to do with human psychology.
chans just happen to be good at the kind of natural selection that lets effective memes bubble to the top. But even before there were chans, what the Left did was (attempt to) create memes. "Republicans are rich fat cats" is a successful meme, and it makes a lot of people avoid the label Republican.
"Teflon President" was an attempt at a meme about president Regan, but it never caught on. They were trying to say that he was corrupt, but nothing ever stuck to him - so, "even though we have no evidence, you should hate him anyway." That's what they tried to say, but it didn't catch on. Unsuccessful meme.
If you have the benefit of the internet but don't have good memes, then the internet doesn't really help you.
The real difference between the mainstream left of the past (and present) and the alt-right of today is how we create memes. The Left has to hire professionals (I'm not kidding) to custom make them, and then they focus group test them. They're slow to make memes and they have a low success rate.
By contrast, the alt-right has a culture where we try dozens of new things each day, and every few months, we find one that is so good that it catches on. Only then does it rise out of the swamp of the chans into mainstream culture. But basically, every one that makes it out of the swamp is a product of natural selection and is "biologically fit" and able to survive in people's minds.
The Left cannot have a culture like that because they're too easily offended. People aren't allowed to try new things. Their instinct is to ban anyone who gets out of line. So, they're only option is the "professional" marketing agencies that invent their memes.