The "lie" was completely transparent. Don't skirt the analogy, if I smashed your room and left those keys, and told you that they did it, who do you think did it?
No matter how transparent that lie was it was still a lie!
You can believe opinions or believe the facts given in the Quran it is entirely up to you..
The definition of Lie is false statement made with intention of deceiving. That's exactly what Abrahim did;
He said to his father and his people, "What are these statues to which you are devoting yourselves?"
They said, "We found our parents worshiping them."
He said, "Indeed, you and your parents have gone totally astray."
They said, "Are you telling us the truth, or are you playing?"
He said, "Your only Lord is the Lord of the heavens and the earth, who created them. This is the testimony to which I bear witness.
"I swear by GOD, I have a plan to deal with your statues, as soon as you leave."
He broke them into pieces, except for a big one, that they may refer to it.
They said, "Whoever did this to our gods is really a transgressor."
They said, "We heard a youth threaten them; he is called Abraham."
They said, "Bring him before the eyes of all the people, that they may bear witness."
They said, "Did you do this to our gods, O Abraham?"
Abraham Proves His Point
He said, "It is that big one who did it. Go ask them, if they can speak."
They were taken aback, and said to themselves, "Indeed, you are the ones who have been transgressing."