You are assuming they don't have a block or a redirect, which would be going onto the cop because there is no reason not to, and also he would likely draw protection so he would have to be busdriven into a kill, which you obviously don't believe happened.
I also think if they feared the cop they would just kill him night 1, similarly if they don't fear a Watcher or a protect then no reason to do it that night.
Ultra on the other hand would have more or less served his purpose getting Poyser out, this goes doubly if Luka is scum because the fear would be him going to his next target which would be Luka. Makes plenty of sense to me.
I'm not saying any of this to convince you as I don't believe you can be reasoned with, in fact you can just stop quoting me please, you're going to look very silly after my flip