I'd go as far as to claim that lying is virtually always unnecessary. People are quick to come up with examples where they think it's the right thing to do, yet when you ask these people when they themselves would rather hear lies than the truth I usually get nothing.

Lying to "not hurt someone" implies that you consider yourself a better judge of this person's ability to manage their emotions. That's not how you treat an adult, especially one you pretend to respect and care about.

However, not lying isn't synonymous with radical honesty either. No need to tell everything that's on your mind - just don't say something you know to not be true. If grandma's cooking isn't to your liking you probably don't need to insult her for it if she asks. I'm sure you can come up with something more diplomatic. If rudeness and insults are the "truth" then than perhaps reflects more on you than on them.