Anslem's argument is sound.

[Mystic]

If you don't value actual life, what do you value?

So this is where it gets tricky, because I'm going to say value to mean one thing, and you think of it as another.

I value donuts.  They are delicious.  I do not value brussel sprouts.  They are gross.  

I don't believe my valuing donuts but not brussel sprouts says anything about donuts or brussel sprouts having any intrinsic value. 

I do value my life.  But in the same way I value donuts.  It's something I like.  That most of us like being alive does not make life inherently valuable.  It's just a common opinion.  Just like most people liking donuts doesn't make them more valuable than brussel sprouts, which are generally despised.  

What I think you need for your argument is a way to show human life is valuable that isn't based on an opinion, as you can see with many examples that opinion of value and intrinsic value (such as with donuts) are not connected.

You may not like brussel sprouts for personal use, but if others do eat them, you should value them for other's sake. And that should value is due to objective standards, they are beneficial for people. And that is based on facts. Whether you like them or not, doesn't take away their value to others.

God knows the benefit of everything with respect to everything and the grand design. No one else knows the value and measurement of things like him. The closest to measuring everything as God is the leader of time, but even his vision is not absolute, just accurate, it is accurate and true, but not absolute like God's.

God knows the secret of your intentions, while many humans, deceive themselves about their intentions and states.

God knows the ranks of our states with respect to each other, and with respect to our potential. We don't know our potential, but God does, at each time, so he is the best of judges.

His vision defines us as we are, his act of creating is by the truth of his vision, which is respect to wisdom and knowledge he has of himself.

You take away the objective value of humans and all that is left is us defining what we are by our mere desires and judgment of ignorance with no reality to our actions.