When people say, "honestly," with the leading word in a question I feel like saying, "What? Do you think I've been lying to you all the other times?"
Another favorite of mine is when people say, "You want to know the honest-to-God truth?" You are guaranteed my response will be, "No. Lie to me."
I think people say 'honest' when they are already unsure about the topic following the word.
They would like some acceptance of the item or thing and need reassurance.
If it is a personal thing, especially, I find being tactful the best way to go.
If the subject seems really ludicrous, like polka-dots and stripes together as an outfit for "The Ball," I would give them the harsh truth.