What does John 15:19 mean?
First Peter 4:4 gives a parallel explanation of this idea. The unbelieving world prefers selfishness and pleasure over honoring God. Part of our sin nature is seeking approval in our sin, especially by reassuring ourselves that "other people do it, too." The contrasting feeling is conviction, which our sin nature responds to with anger. In the modern era, biblical faith is slandered as evil, hateful, fearful, closed-minded, or ignorant—all deeply ironic and hypocritical criticisms. Despite their own demands to "tolerate," the non-believing world levies hate at Christians who don't conform (Romans 12:2; 2 Corinthians 5:17).The idea of being called out by God as separated people (1 Peter 2:9), chosen for something more honorable than sin (2 Timothy 1:8–9), makes Christians offensive to the unbelieving world. When Christian believers don't join in worldly sins, the world responds with hatred and mockery. Choosing to honor God shines an uncomfortable light on sin, and that "earns" the hatred of the world. Jesus' words here are meant to reassure Christians that persecution for faith is a sign that we're identified with Him. When we act in truly Christlike ways, and suffer for it, we can take comfort in knowing that it's further proof of the validity of our beliefs (Acts 5:41).
In this passage, Jesus speaks only of hardships that come as a result of following His teachings (John 15:20). Christians who act in unChristlike ways, and suffer the natural consequences as a result, can't interpret those consequences in the same way (1 Peter 4:14–15).