>* My position is that emotional manipulation leads to a worse understanding of the world and decrease net welfare by encouraging people to be less rational.*

That's circular reasoning. "Emotional is bad because it's less rational" (given that rational is the opposite of emotional).

Why would emotional be worse? Or generally worse? It is itself a useful way of deciding, that originated from evolution. In fact there would be a thing as being too rational. Besides, if the ultimate goal is one's happiness (and rationally, there's no way to objectively establish any other goal over it), that's something inherently tied to emotions anyway.

Here's some food for thought:

The classic argument is that those of our ancestors who saw more accurately had a competitive advantage over those who saw less accurately and thus were more likely to pass on their genes that coded for those more accurate perceptions, so after thousands of generations we can be quite confident that we’re the offspring of those who saw accurately, and so we see accurately. That sounds very plausible. But I think it is utterly false. It misunderstands the fundamental fact about evolution, which is that it’s about fitness functions—mathematical functions that describe how well a given strategy achieves the goals of survival and reproduction. The mathematical physicist Chetan Prakash proved a theorem that I devised that says: According to evolution by natural selection, an organism that sees reality as it is will never be more fit than an organism of equal complexity that sees none of reality but is just tuned to fitness. Never.

http://www.theatlantic.com/science/archive/2016/04/the-illus...