Some people will contend earnestly for nearly every opinion they have. Others will contend earnestly for extraordinarily little if anything.
A willingness to engage in verbal conflict over matters involving your opinions or manmade religious traditions and teachings is not what Jude exhorted his beloved readers to have.
A willingness to engage in verbal conflict over “the faith which was once for all delivered to the saints” (v. 3) is what Jude exhorts us to have.
Since we did not live in Jude’s era, it ought to be impossible to confuse our opinions with the faith delivered in the first century A. D. There are nearly two millennia between the two.
Since almost all of today’s manmade religious traditions and teachings were non-existent in Jude’s day, it ought to be equally impossible to confuse them with the faith delivered in the first century A. D.
Biblically speaking, there is only one faith (Ephesians 4:5). It is “the faith” (Jude 3). It is found in the word of God (Acts 13:7-8).
Like Elymas the sorcerer, there are those who seek to turn others from the faith (Acts 13:8). They are full of all deceit and fraud; they are the offspring of the devil; an enemy of righteousness who cease not seeking to pervert the straight ways of the Lord (Acts 13:10). Later in his epistle, Jude will call these ungodly men: dreamers, spots (i.e. stains) in your love feasts, clouds without water, fruitless autumn trees, raging waves of the sea, and wandering stars for whom is reserved the blackness of darkness forever (vv. 8, 12-13).
Beware of and contend earnestly with these ungodly men who seek to turn the grace of God into license to sin and deny the authority of the only God and Jesus Christ (v. 4).