First off, it is really easy for value to life to outweigh extinction. If the aff concedes you have a 100% internal link to value to life (i.e: no defense) then it does't really matter if we die since theres no point to live. Thought experiment: I've invented a black box, if you go inside the box you get to live forever, but if you go in the box you don't experience anything. What this means is you can't feel, smell, see, hear, or talk to anyone. It's complete pitch blackness with no sensory perception. Is that really a life worth living? Probably not.
Second, my rant. V2L is such an underused debate arguement. Its really fucked up because its actually something we all need to consider - what does it mean to live a worthwhile life? The problem is that since debate has become so extreme i.e: everything=extinction forever x 100, its really hard very V2L to outweigh that bullshit, which makes all value to life claims really fucking stupid since its all like, "Capitalism means I can't do what I wanna dooooO! NO VALUE TO LIFE FOR ME!".
The real question is: would you sacrifice some of your liberties (freedom of speech, expression, assembly) or even sacrifice PARTS of them to make your life .001% safer.
When people say the War on Terror is bad because it cuts into civil liberties they don't mean it destroys ALL LIBERTIES, what they are saying is that the amount of security the war on terror brings is negligable because it makes a wortwhile life LESS worthwhile in the process.
Basically what all this ranting means is that if you wanna go for Value to Life, your impact calculous needs to be centered around probability first and timeframe secondary.
EDIT: The only time I've heard an 'ontological damnation' arguement sound convincing is when its been explained like v2l, hope this helps.