Why bhai gurdass ji calls Guru Nanak as God?
my understanding
imagine a situation ,hypocrisy at its best in society
rituals ,crimes being done in the name of religion and to satisfy so called GODS.
Rapes,Murders ,theft ,robbery all in the name of religion
Poor people who are more into their lives and hard work than to worship gods are being tortured in the name of religion maybe asking what wrong we had done to face such a wrath from the so called GODS of such religious people.
Poor Lady whose husband died due to circumstances had to set herself fire in the name of SATI and many countless rituals.
At that time Guru Nanak was born ,and with his very common sense ,courage and his wisdom he took on such hypocrisy.Fearless was he ever.
He showed the path to many people and showed how true service is to be done,how love for equality and fellow beings are the best deeds if to be done in the name of religion.
Bhai Gurdass Ji acknowledges all this for Guru Nanak,out of love of highest order for Guru Nanak Dev Mahraj he says so.
Many youngsters call each other love partners as "RABB",some call their fathers,mothers as GOD.
There is even a famous quote which says "i havent seen GOD but i have seen MOTHER.
my understanding says that calling Guru nanak dev ji god is just an expression out of love nothing else.
In Guru Granth Sahib Ji Guru Nanak Dev ji humbly calls himself servant ,never makes such statement.
Sorry if i say something wrong,pardon my unintentional mistakes
Here a song by rahat fateh ali khan acknowledging mothers more than GOD
Rab Kehn Nalo Pehla Maa Kehna Sikhya - YouTube