Is it permissible not to enjoin against evil using obscenities, especially if the anger is for the sake of Allah? And how should one deal with those who curse religion, particularly if they are uneducated or from the common folk? And is gentleness effective with them?

Anger for the sake of truth is commendable in its proper place, but cursing and reviling are forbidden. Anger for the sake of Allah does not justify obscenity. Enjoining good and forbidding evil is a religious obligation, but it is not permissible to use obscenity therein. One must be endowed with forbearance and gentleness, for knowledge, gentleness, and patience are essential for one who enjoins good and forbids evil.