I look at it this way. The most fundamental aspect of the game is in townies trying to ferret out scum, while the scum are attempting to hide their identities. Scum have something to hide. Townies, barring edge cases, have nothing to hide. It would take an incredibly talented scum to maintain a perfect townie facade for an indeterminate length of time.
DA claimed he voted for himself in an attempt to demonstrate his point: that scum would hammer him even in this game. As such, if a townie, he was offering himself for sacrifice in order to cast heavy suspicion upon those who hammered him -- clearly in the expectation that some scummer would be stupid enough to pull the trigger, be instantly lynched, and keep scum from hammering for the rest of the game.
The flaw with this logic is that he's right: only an idiotic scum would hammer in this position. All that would have to be done would be for them
not
to cast the lynching vote, and it would appear as if DA had been proven wrong -- all scum would now be in much less danger when hammering. Allowing this to happen would clearly be detrimental to the town.
The only beneficial outcome, at that point, would be and some idiot scum
did
off him, which would not take any heat off the scum. Against this, there were two possibilities: DA was a scum, and would live, clearly a negative. Or, he was innocent and I could cast the killing vote, which would definitely not be as positive, but would be alot less negative than allowing scum to prove him wrong. The absolute worst case scenario would be that DA gets lynched and an innocent party gets lynched the next day. But even should that occur, we will still have more "lives", as noted above, and by that point remaining townies should have a very good idea who is or isn't scummy, based on what's been posted in the discussion that would be sure to ensue.
I was hoping this would be inferred, and I wouldn't have to elaborate on it, in order to minimize the chances of altering scum behavior, but an explanation was demanded, so I'll give one.