This article can be summed up fairly succinctly:

1. All current religions promote a recognisably similar moral code

2. Humanism promotes a similar moral code

3. Therefore humanism derives its moral code from religion

This argument can be further summarised as:

1. For All X, X implies A

2. Y implies A

3. Therefore Y is an X

A moment's thought shows that conclusion 3 does not follow from 1 & 2. See:

1. All acids contain hydrogen

2. Water contains hydrogen

The inference "3. Water is an acid", is not valid