As someone who plans to adopt kids rather than adding another human to an overcrowded planet, people who act like life is meaningless without reproducing strike me incredibly narrow-minded.

A third point as well -- humans are not manifest destiny. There is no imperative for our continued existence in this universe, so we have no obligation to reproduce -- any reason to reproduce you can think of is imagined by a brain evolved from millennia of creatures that decided to reproduce: selection bias.