I think you interpreted the article in a way that was not intended.
I don't think the author want people to be totally honest always, like, "Hi dear colleague. I think your dog is stupid. And, by the way, you are, too."
Instead, I imagine that fairly many people tend to, when their friends say "Do you want to hang out with us doing this?", they answer "yes" just to please their friends. Although in fact they might have wanted to suggest something else instead. And in these cases, the advice in the article can sometimes? often? be useful. I.e. to be more transparent and honest with your friends about what makes you happy.
If you interpret a piece of advice with the mindset that "perhaps this is good advice in some situations, when might that be?", then it can be helpful and useful to you (or to other people — to me, when I was younger, for example).
But if you interpret it like "always do this", then a piece of advice that is actually good in some situations, has been lost.
(I suppose the article can be rewritten / reworded, to make it easier to interpret it in a "good and useful" way.)