Diplomatic people are not necessarily dishonest as is being indicated. They just have a different way of putting their point across than one who is more straight forward, the former doing so in a manner that deals with the issue in a more sensitive and thoughtful manner.
As for the stakes in a popularity contest, I don't think there is anything like that. From one context to another, it will more likely be as to what is acceptable and what is not. In one scenario, it will be greatly liked that the person was blunt and straight forward, while in another scenario, the person at the receiving end will be glad that the matter was dealt with tactfully. In the case of a really close friendship or other relationship, neither should affect the relationship. In the case of certain kinds of relatives or in an office workplace, relationships can and do get affected. Thus it is not a matter of popularity, but of the end result.
When people come at you with their worst, you should come at them with your best (advice given to Selena Gomez by her mother, quoted in Time magazine.)