Verses 20-21 show that first there must be self contention and spiritual fortification by keeping ourselves in the love of God. Loving god is the first command to keep above all else. Not all should be dealt with the same way. The goal is to save souls not to destroy souls. Jude s letter is harsh and strong because the sin is harsh and ruthless.
Creepers are dangerous.
And worse yet, they are in our midst unawares. They infiltrate congregations representing themselves as believers. They must be recognized and neutralized to minimize if not prevent their destructive influence. Nonetheless, we must be wise, cautious, and compassionate. We are called to win the lost to Christ.