This is both dumb and dishonest. It's dumb because you're not making an actual argument, just pointing at a potential long-term outcome, which isn't even an obviously bad outcome; if there are no more humans, there are also no humans to fret about their own lack of existence, so who exactly is being harmed here?
It's dishonest to claim that a temporarily shrinking population (which is a good thing given our current population level) will automatically lead to extinction. It will absolutely not.
You sound like somebody with some kind of religious conviction, which is fine for you, but leave the rest of us out of it.