Preservation of the Sikh Guru Granth vs the Quran... really?!

This video is in response to a Sikh named Damans who participated in a discussion on the @DawahDigest Youtube channel, and during which attempted to raise doubts against the preservation of the Qur'an: https://www.youtube.com/watch?v=3t2yU0qRWjE

Except that he, and Sikhs like him, need to recognise how fragile the glass temple is that they're residing under when questioning the preservation of other scriptures. Here's a small taster of exactly how fragile their house really is. As for a more thorough examination, he would do well to read our article on the inauthenticity of the Sikhism's most celebrated manuscript, the Kartarpuri Bir: http://www.islamsikhism.com/kartarpuri-bir-pothi