An Excerpt from Bhai Manvir Singh's blog:
... I love listening to Keertan and Katha (discourse on Gurbani). It was Bhai Veer Singh Jee Delhi Wale's last evening of Katha at Park Avenue Gurdwara. I mentioned his Katha in a previous post.
Bhai Sahib's Katha on Saturday was on the topic of "Nindiyaa" (slander). Bhai Sahib gave a beautiful description of what Nindiyaa is and how it doesn't have a negative effect on the devotees of Waheguru.
"A rose plant also grows thorns. What is "Nindiyaa" (slander). Nindiyaa is not recognising the roses on the plant and instead saying it is plant of thorns.
We all have "avguns" (negative points) saying something bad about someone becomes slander when we make someone out to be fully bad, and see no good in the person whatsoever, i.e. bad through in through.
However, no-one is perfect, only the Guru and Waheguru are Perfect.
Hence doing Nindiyaa of anyone is bad, defining someone is through and through bad and not recognising the even smallest amount of good quality or virtue in a person is considered Nindiyaa.Gurbani says:
ਨਿੰਦਾ ਭਲੀ ਕਿਸੈ ਕੀ ਨਾਹੀ ਮਨਮੁਖ ਮੁਗਧ ਕਰੰਨਿ ॥
nindaa bhalee kisai kee naahee, manmukh mugaDh karann.
It is not good to slander anyone, but the foolish, self-willed manmukhs still do it.
ਮੁਹ ਕਾਲੇ ਤਿਨ ਨਿੰਦਕਾ ਨਰਕੇ ਘੋਰਿ ਪਵੰਨਿ ॥੬॥
muh kaale tin nindkaa, narke Ghor pavann. 6
The faces of the slanderers turn black (in this life & the next), and they fall into the most horrible hell. 6(Ang 755, SGGS)
The saintly people actually appreciate Nindiyaa.
They don't lose anything through people slandering them. This is because the wise person uses people's slander to self-analyse himself or herself and correct his or her "avgun" (negative points) and convert them to "guns" (virtues).
However, the Nindak (slanderer) is stuck in slandering and forgets self-correct and improve his own jeevan (life). Hence, the wise saintly people win against the Nindaks.
ਹਰਿ ਜਨੁ ਰਾਮ ਨਾਮ ਗੁਨ ਗਾਵੈ ॥
har jan raam naam gun gaavai.
Waheguru's humble servant sings the Glorious Praises of the Waheguru's Name.
ਜੇ ਕੋਈ ਨਿੰਦ ਕਰੇ ਹਰਿ ਜਨ ਕੀ ਅਪੁਨਾ ਗੁਨੁ ਨ ਗਵਾਵੈ ॥੧॥ ਰਹਾਉ ॥
je ko-ee nind kare har jan kee, apunaa gun na gavaavai. 1 rahaa-o.
Even if someone slanders the Lord Waheguru's humble servant, he does not give up his own goodness. 1Pause(Ang 719, SGGS)