There are 2 possibilities:
a) The Muslims contributors to Guru Granth Sahib were not in fact "real" Muslims, in which case Sikhs need to stop referring to them as such when trying to prove Sikhism's "openness" to non-Sikhs, you then no longer have the right to state that Guru Granth Sahib has any Islamic writings within it's pages, or...
To start with, Guru Granth Sahib does not have any Islamic writings in its volumes, nor has anyone ever claimed so, that would be like diluting the philosophy of Sikhi, which in its pristine form, is unique of the Abrahamic and Dharmic religions.
b) Farid, Kabir and the rest WERE "real Muslims" (not committing shirk), in which case, I would like to ask the SPN members who seem to think that Muslims are brainwashed, that Islam makes people brain dead, why they are proud to have the writings of these brain dead men in their holy scripture? Why they are proud to have one of these brain dead men lay the founding brick of the Harmandir Sahib? And most importantly, what they think of Guru Nanak Dev Ji, who for some reason decided it would be a good idea to have one of these brain washed men as his best friend and most trusted companion. Reading through this thread, it is obvious who these members are.
Either way, you can't have your cake and eat it too.
I don't think all people of any community are either 'good' or 'bad' in totality. But it is most frequently the visible majority of that counts, and that is what gives rise to the stereotypes.
That is not to miss the fact that the burden of the terrorizers should not be heaped upon the shoulders of the innocent Muslim who walks a couple of blocks down the road to share Christmas festivity with his friends. That would be just injustice. I wouldn't put Malala Yousafzai and Talibani terrorists on the same bus.
Talking of Islamic terrorism, it is not a new phenomenon, it existed even during the times of Ghenghis Khan, Babur and Aurangzeb, then they were called invaders and oppressors, and now they are called terrorists. What is unfortunate is that the Muslim clergy, the Qazis and Imams have played in the hands of this divisive forces all the time long, and not without their own agenda of furthering their interests.
So, were
Kabir, Farid, Bhikhan or
Mardana 'brainwashed' like the Islamic invaders of that time? Surely not. Instead, they constantly raised the bar of communal tolerance with their all-inclusive philosophy. But that does not absolve the larger part of Muslim community from the blot of terrorism and oppression of minorities that has often taken place under Islamic and Shariah rule.
Neither Islam is bad, nor are all Muslims bad. But, I would still say the Muslim community needs to do a lot more homework at tolerance and Universal brotherhood, and actions speak louder than words; just opining that 'Islam means peace' is simply not enough!