What is the ruling on defending someone who commits a haram act?

A Muslim must support his Muslim brother, whether he is an oppressor or oppressed. Supporting him when he is an oppressor means restraining him from his oppression, forbidding him from it, and commanding him to repent, especially if one loves him; for true love entails cooperation in righteousness and piety.

As for defending him by downplaying his forbidden act or denying its prohibition, it depends on the type of forbidden act: whether its prohibition is known by necessity or if there is a difference of opinion regarding it, for forbidden acts are not all alike.

To rule accurately, the forbidden act and the manner of defending it must be clarified.