This kind of doubt is totally wrong, and also against the spirit of the age. This age is the age of respect and tolerance. We are distributing the Quran on a large scale, and our distributors have never reported such an incident. On the contrary, our distributors tell us that those who are given the Quran receive it with great respect and thankfulness. According to our knowledge, all those so-called events of disrespect were nothing but rumours. Muslims acted against those events of disgrace of the Quran without inquiring into them. This reaction by the Muslims was quite against the teaching of Islam. According to the Quran, no action is allowed before making a thorough inquiry into the event. This commandment is mentioned in this verse: "Believers, if an evil-doer brings you news, ascertain the correctness of the report fully, lest you unwittingly harm others, and then regret what you have done." (49:6)
It is a hypothetical question that if a non-Muslim disgraces the Quran, the responsibility for it comes on the Muslim who had given the Quran to him. But for the sake of argument, I can say that if an event of this sort happens, Muslims will never be accountable. There is a very clear verse in this regard in the Quran: "Believers, take care of your own souls. The misguided cannot harm you as long as you are guided." (5:105)