There is plenty of resources to support humanity.
I cannot say I agree, and I think I recall that some indicators currently suggest we'd need about 3 planets to keep going at the same pace.
I think we shouldn't use up every atom on Earth to churn out more humans. Our species has experienced a massive population explosion and is at peak numbers.
Usually this kind of events are followed by a hurtful population crash. It seems considerably better if growth ends due to a (subconscious?) decision to stop expanding, rather than a war for remaining resources.