The letter of Jude is a short one chapter letter full of practical instructions for the early church. Th Christians were beginning to become organized as a separate religion and already outside influences and power struggles, which are so mush a part of human nature, are setting in.
Jude tells us to use "our Holy faith" as our foundation, to instruct others in correct living and to "wait for the mercy of the Lord." The Catholic church is always very humane and practical in its pastoral teaching. Human weakness is always allowed for.
We should apply the same loving gentleness to ourselves and our friends; our judgments should never be too harsh and we should always be looking out for the spiritual welfare of our friends and for their general well being.
This sounds like common sense now but at the time of Jesus it was revolutionary. And you would not have to look far in today's world to find communities and mindset where such thinking would still be revolutionary.