What do you think of this social project?

I'm not sure about that hypothesis. People have negative emotions no matter what environment they live in and were brought up in. Demonising negative emotions isn't going to make people learn to be happier - it's going to make them feel guilty for not being happy which will in turn make them feel worse. It's a vicious circle. You can train behaviours, but I don't think you can train people to feel emotions since emotions are so much more complex and they're not conscious; I can't just snap my fingers and decide to be happy or sad or angry regardless of whether I want to.

At the most basic level emotions are chemical reactions to stimuli, and you can't control the your body's chemical reactions to stimuli. Not allowing people to feel perfectly natural emotions without guilt is repressive not matter which way you look at it and it causes huge amounts of stress.

How about instead of repressing people's negative emotions, you teach them about the benefits of positive thinking? Allow people the freedom to feel negative, and instead of demonising negative feeling you can be more positive yourself and show the benefits of positive thinking.