Fair means the rule still applies when it’s your friend who broke it.

Rules are easy to enforce against strangers, and that is not enforcement, it is convenience. The test arrives when applying the standard costs you something: a friend sent off, a teammate’s point disallowed. Most people quietly keep two versions, one for the people they care about and one for everybody else, and everybody can see which they are being given.

When it is your friend this week, say the same thing you would have said about anyone. Then stay their friend, which is the part people forget is available. Being fair does not require being cold about it.