That is certainly true mh that calling yourself a humanist does not carry with a stigma like most other isms. But the point Professor Gray is making is that it is not logically consistent to hold to humanism and a strict naturalistic or secular worldview. Humanism is injecting properties that are non-existent in such a framework which is why he identifies it as the new religion of a post Christian Europe and parallels it to the ideas in Christianity.
We are not made happy by what we acquire but by what we appreciate.