These are two factions of extremist Hinduism trying to influence/destroy our religion.
They have been altering our literature for many decades now, trying to influence people to believe that we are somehow a part of Hinduism. This could not be further from the truth.
Guru Nanak Dev Ji, the Sikhs first Guru and founder was indeed born to a hindu family. Just like Jesus was born to Jews and Mohammed was born to pagans, this does not mean that they followed their parents views on spirituality.
Numerous times within the Guru Granth Sahib Ji, our present Guru it says that everyone is equal, and that Brahmins rituals ways are false. Guru Nanak Dev Ji did not embrace the "sacred thread" ritual that was presented to him by his family, saying that he wanted a thread that would never break and go with him to the next world.
Guru Gobind Singh ji, our 10th Guru clearly states in our everyday evening Bani that:
"raam raheem puraan kuraan anek kahai mat eik naa maanyo."
"The Puraans, the Hindu scripture, praise and glorify Raam, and the Quran praises and glorifies Muhammad. Likewise, other religions talk of of their own prophets and glorify them as God. I do not accept any of these. "
However, due to our lack of understanding of our religion some of our people are falling pray to this and actually believe that Guru Nanak Dev Ji was given his power through some Hindu
I say it again, we must educate ourselves otherwise we will fall pray to "backdoor" attacks like these on our religion.
It is important to understand that I do not dislike Muslim or Hindu people, in fact I have a lot of respect for anyone following their chosen path to God. What I dislike is people trying to manipulate our religion, and our own people not having the knowledge to do anything about it.