I have always considered it this way:
A town-directed kill has some possibility of hitting scum. A scum-directed kill has 0 possibility of hitting scum. We want to maximize the number of town-directed kills in order to maximize the chance that we hit scum. This means (IMO, which not everyone shares) that town should (generally) take every kill they can. Determining when town should NOT take a kill that it has the opportunity to take is really where parity comes in.
In role madness, there are undoubtedly ways for town to disrupt parity. Because town can disrupt parity, all parity arguments are essentially meaningless, and we should take every kill we can get, because that maximizes our win potential. (again this is my OPINION. There are potentially some unquantifiable gains from not lynching/not killing. Galzria/Robz love the argument of "keeping town voices alive". I believe that the quantifiable gains of extra town-directed deaths are greater than the unquantifiable gains of "town voices"...but since the latter is unquantifiable, it really may be bigger. I acknowledge this, I just don't believe it.)
(For those unaware, here's the parity stuff. Simplest case:
-4 players, 1 scum (i.e. 3 town). If town is lynched then there are 2 town v. 1 scum. Scum kills one of the town players, and scum wins. Each town player has a 1 in 3 chance to find the scum.
-IF one of the town players is eliminated first then there are 2 town v. 1 scum. Each town has a 50/50 chance of getting the scum. if town is lynched, scum wins. Thus, it benefits town to no-lynch and force scum to kill one of them off.
BUT this argument assumes that the town players can't stop the kill, or kill at night. If one of those 2 unkilled town players is a doctor or vigilante, then the 3v1 situation has potential to be better for town. A vigilante can shoot after the kill, this gives a 50/50 chance in ADDITION to the ~1/4 chance of the lynch. If one is a jailkeeper, he can save the night kill and get the advantages of both days (if he himself isn't killed). If one is a doctor/roleblocker same thing except guaranteed to find scum if they survive and choose correctly.
So, that's why I said that parity doesn't apply.)