It's called context. The beginning of the chapter is Elijah (Elisha's master) being removed from Earth and going up (using the exact same Hebrew word) to Heaven. Considering that the thugs are clearly not pious people, "remove yourself from the world, like your master did" has only one viable interpretation.

As for my choice of the word "thugs" ("mob" would be another good word), that is necessary to preserve the connotation. Remember, there were 42 of them punished, possibly more escaped - this is a threatening crowd size (remember the duck/horse meme?). Their claimed youth does imply "not an established veteran of the major annual wars", but that's not the same as "not acquainted with violence".