In his story "Abel Sanchez," writer Miguel de Unamuno nicely highlights the nature of envy and why it is that the envied person is often trapped by his envy. In his writing he retells the story of the Cain and Abel, and he modernizes it. The Cain character is played by a skilled surgeon who has for years secretly envied his friend, Abel Sanchez, a skilled artist. At one point in the story, the doctor is scrutinizing one of Abel's paintings. This particular painting is a depiction of the Cain and Abel story itself from the Bible. At first, the doctor is convinced that the face of Cain in the painting is modeled on his own face. And he becomes furious! How dare Abel Sanchez use HIM as a model for envy? The gall! The nerve! The implied accusation! But then, upon closer inspection, the doctor decides it's not his face after all. Does this defuse his anger? By no means! Instead the surgeon becomes irate that Abel Sanchez did NOT deign to use him in one of his famous paintings! How dare Abel NOT use his face!
De Unamuno's point is clear: when you are the object of envy, you cannot do a blessed thing to make the situation any better. Try to be extra kind to the one who envies you, and this kindness will get written off as condescension and charity. Try to rise above things by ignoring the one torn up with envy and you will be written off as arrogant and rude, thereby merely confirming the envier's low opinion of you. Neither approach nor avoidance can help the envied one.
It's difficult to know how much of a role envy plays in Mark 6 but surely the sneering attitude of Jesus' fellow townsfolk revealed at least a smidgen of envy-driven sentiments. Maybe this had something to do with his inability/unwillingness to do miracles there. He was doomed no matter what he did. Do more miracles, and the people write him off as a showboat (and/or as someone drawing off power from dubious sources). If he refused to do miracles, maybe a few would say, "What now?! We're not good enough for you, not WORTHY of your wonder-working power!?"
Perhaps the only thing left to do was leave town and go to other villages, from which Jesus sent forth his disciples to do wonderful work in places where it could be appreciated.