That is an argument of the pessimists and enemies of the good.
Pessimism is clearly irrational: Look at the world we live in; look what humanity has achieved since the Enlightenment, and in the last century - freedom, peace, and prosperity have swept the world. Diseases are wiped out, we visit the moon and (robotically) other planets, the Internet, etc. etc. etc.
To be pessimistic about our ability to build a better world is bizarre.
We're not talking about hypotheticals - we can always construct hypotheticals that yield the answer we desire - but the real world.