You simply don't get away with embarrassing some of the show's most beloved characters without getting put in your place.
In the last season, Sebastian has managed to slight Daryl, threaten Rosita, and make a mockery of Eugene and no one has been able to do a darn thing about it because of his high standing in the Commonwealth as Governor Milton's son.
It's extremely frustrating because he's proven time and again that he doesn't care about anyone but himself in the zombie apocalypse.
In the last block of episodes, we learned that Sebastian horrifyingly sent over 30 citizens of the Commonwealth to their deaths in the hopes they could retrieve some cash for him. You read that right, cash. No one truly needs money in a zombie apocalypse.
A Sebastian death would also deliver justice for comic readers. It was beyond disappointing to read that Sebastian survived the "TWD" comic after shooting the story's protagonist, Rick Grimes, dead as he lay defenseless in bed.
Sorry, Sebastian, but you just don't have any redeeming qualities here or in the comics.