SB 3.16.5

yan-nāmāni ca gṛhṇāti
 loko bhṛtye kṛtāgasi
so ’sādhu-vādas tat-kīrtiṁ
 hanti tvacam ivāmayaḥ
Synonyms: 
yat — of whom; nāmāni — the names; ca — and; gṛhṇāti — take; lokaḥ — people in general; bhṛtye — when a servant; kṛta-āgasi — has committed something wrong; saḥ — that; asādhu-vādaḥ — blame; tat — of that person; kīrtim — the reputation; hanti — destroys; tvacam — the skin; iva — as; āmayaḥ — leprosy.
Translation: 
A wrong act committed by a servant leads people in general to blame his master, just as a spot of white leprosy on any part of the body pollutes all of the skin.
Purport: 

A Vaiṣṇava, therefore, should be fully qualified. As stated in the Bhāgavatam, anyone who has become a Vaiṣṇava has developed all the good qualities of the demigods. There are twenty-six qualifications mentioned in the Caitanya-caritāmṛta. A devotee should always see that his Vaiṣṇava qualities increase with the advancement of his Kṛṣṇa consciousness. A devotee should be blameless because any offense by the devotee is a scar on the Supreme Personality of Godhead. The devotee’s duty is to be always conscious in his dealings with others, especially with another devotee of the Lord.