Dexter - Possible Spoilers

[Soda Popinski]

Originally Posted by Buzzkill Anyone else think it's odd that they are just turning Dexter into a unprincipled killer? He just murders an innocent guy so he could ensure that he murders another guy that would have likely been dealt with by the law? Used to be he'd only off people if the law couldn't handle them - but john lithgow is about to go away for life, possibly be executed anyway. Dunno seems weird to me

The trucker killed a hooker or something but the evidence was contaminated and he got off without any charges.

It doesn't ensure that he murders Arthur. It just gets the police off Arthur's trail at least for a little while until Dexter can kill him. And he wants to kill him because Dexter takes it personal. He wants to kill Arthur himself. That is why he saved him from the suicide attempt and also from the police.