I agree with the premise, although his conclusions are a little bit like a conspiracy of one side (the side he does not like) against the other. The truth is this is used by all political parties, in fact, it is used by the media in all their reporting (non political and political) - just look at the coverage of whatever the next big crisis is (environmental crisis, children on social media crisis etc.) and it also used by charities and companies in television advertising. Why? because it works.
There is also a view that parties/people win elections not on policies or manifestos but on who is able to control the agenda. They even use the term "narrative". i.e. parties do not put policies in their manifesto that are designed to help the country but are designed to allow them to control the narrative. That is why in government parties renege on manifesto promises - they are not designed for government. Obama was able to do this in his election campaign and Trump was able to do this more successfully than Clinton in his election campaign.
What is more fundamental is why does this work? For that you need to look at our evolution and genes. A relatively new area of research is how 2 groups of people with exactly the same facts on an issue can come up with 2 completely different conclusions. Both are certain that their view is the right view.
For analysis of our evolution and genes, in terms of why most western democracies has a left wing party and a right wing party have a look at this.
https://www.youtube.com/watch?v=W8N3...sj7ITD&index=1
It is one of three videos but it is worth taking the time to watch.