I'll tell you why I think Spak should live. Everyone knows what his motivation is. Revenge. Plain and simple. The double agent failed and was exposed. His plan clear and in the open. Since Spak knows victory is impossible, he's going to get revenge and do damage on the rival mafia that did this to him. That is why if Spak lives tonight, it is a boon for the townies since he will be a hunter with them. Moreover, he has been very honest in his intents. He willingly revealed himself as mafia knowing it would mean his death. But he did so to let everyone know where he stands.
Your intentions have been murky and unclear. You have said to kill Spak to prevent his hit. Then, you will become a rival mafia and your own mafia will have to kill you next. That is just wierd. You are going to reject staying in a four mafia strong alliance for no other reason than to force them to kill you? What? Moreover, we know Spak gets his hit regardless. If you become mafia does that mean you would have a chance for a hit also that day? If so, it helps the NWR. Moreover, since the mole didn't work, you have been increasingly desperate to get people to listen to it. You post that you believe the mole even though just yesterday you were ready to examine Mario's voting patterns. You post in the mole thread to get people to listen to the mole again. Then, when people start voting for you, you use my logic lie. Finally, Spak basically comes out and exposes you. Then suddenly, you are willing to tell us your true identity but begin fighting a new arguement. Through all of this, the only thing we have gained about your motives is a desperation to keep people from listening to Spak and have them kill him but not kill Ceric.
What do you care if people kill Ceric? If Ceric is a townie, he has to die at some point for your mafia to live. If he's a townie and the viglante kills him, that's the end of the vigilante. You should be endorsing Ceric as mafia if he is innocent. His death benefits your chances of a mafia victory. But instead, you have rallied hard for Ceric to live.
And finally, we cannot stop Spak's hit tonight. So, why should we kill him? If he is lying to us and does kill a townie with his hit, what can we do now? It can't be stopped. Plus, tomorrow he will be unable to do anything. But, we can stop you from gaining this mafia power, we can verify if he was right about Ceric and we can slow the NWR mafia by letting him live through the night. That is something you are trying to prevent. That is not working for the townies.
There is one final benefit to Spak living the night. He can investigate one person tomorrow. He may yet discover the remaing mafia member. That is soething else you would be desperate to prevent because you are looking out for the NWR. It's what all the evidence leads to.
That is why I support Spak.