They need to make up their minds. Do prefer to be lied to or do you prefer the truth? I'm not saying honesty should be used as an excuse to be rude and insult people, but when the time calls for it we shouldn't hesitate.
Give me a context.
There is such a thing as tact. For example, I'm not going to tell my friend I think her shirt is ugly. That would just hurt her. But if she asks my what she should where to a function, I'll suggest something else.