Long ago the scholars observed:
Fault-finding is not backbiting in six situations—
a wronged person,
one whose identity must be clarified,
someone about whom people must be warned,
an open sinner,
a seeker of a legal ruling,
and anyone requesting help to remove an evil.

One of these grounds alone would be enough to justify a reply such as this; how much more so when several of them coincide—especially the first. The proof lies in the words of Allah, the Exalted:
“Allah does not like the public mention of evil except by one who has been wronged; and Allah is All-Hearing, All-Knowing.”

And in the saying of the Prophet, peace and blessings be upon him: “The procrastination of a solvent debtor makes his honor and punishment lawful.” (1)

The poet said:
To set down kindness where the sword is due
is as harmful as unsheathing the sword where kindness should be.

I ask Allah, Exalted is He, to protect us from injustice and from disparaging people without right, and to make what I write a defense of the sunnah of the Prophet and the way of the righteous forebears. Truly, He is All-Hearing, Ever-Responsive.

Muḥammad Nāṣir al-Dīn al-Albānī