There are several issues with this type of justification.
1) We do not value human beings based on whether they are net positive or negative contributors to societal resources.
2) We do not value human beings based on whether they are net positive or negative contributors to societal resources. (This point is rather important, I wanted you to read it so I included it twice).
3) Babies and elderly are a drain so why not give them the same treatment? If your answer is "because babies will eventually become contributors and elderly once were" then consider the following:
4) Many of these refugees are from war-torn countries, they have few resources of their own and perhaps little education. It might take a generation or two before they fully come into their own and contribute to society in the same way that many other immigrant groups have in the past. Give it time, and they too will contribute.