pujito bhagavan visnur janmantara satair api
prasidati na visvatma vaisnave ca apamanite
(Hari Bhakti Vilasa 10.315, from Dvaraka Mahatmya, conversation between Prahlada Maharaja and Bali Maharaja)
Any person who has criticized a Vaisnava, such sinners, even if they worship Lord Sri Visnu, the source of the whole world for hundreds of births, with such insulters of Vaisnavas, Lord Hari does not remain happy.
Skanda Purana lists six kinds of Vaisnava aparadhas (offenses):
hanti nindati vai dvesthi
vaisnavan na abhinandati
krudhyate yati no harsam
darsane patanani sat
(1) Killing or physically harming a devotee
(2) Criticizing or blaspheming a devotee for:
(a) having a body born in a low family (listed in Upadesamrta)
(b) having a body with a bad complexion (listed in Upadesamrta)
(c) having a deformed body (listed in Upadesamrta)
(d) having a diseased or infirm body (listed in Upadesamrta)
(e) having traces of sins or imperfectness listed in previous sinful life(s) (listed in Harinama Cintamani)
(f) having an accidental or momentary fall down (listed in Harinama Cintamani)
(3) Being envious towards a devotee
(4) Not offering obeisances to a devotee
(5) Become angry towards a devotee
(6) Not becoming happy on seeing a devotee
