That's true whether it's an unlabeled humanism, a "secular" humanism, a "Christian" humanism or something else.
I enjoy reading the often-insighful, almost-always-stimulating long-form blogging of R.Joseph Hoffmann.
With his background, per his Wikipedia link, he's well positioned to comment on Gnu Atheism, the academic study of religion and issues of humanism and philosophy in general.
I largely agree with his take on Gnu Atheism, especially concerns over its combativeness, narrowness of focus and evangelistic propensities.
On larger humanistic issues, I agree with concerns about "scientism," especially but not only found in some Gnu Atheists, and beyond that, a move beyond the classical and Renaissance devotion to the arts.
But, at times, he seems to come close to a false dilemma, positing that one must focus more on the arts and less on science -- science, not "scientism."
Let's take one matter where science, philosophy and overarching humanist principles meet: consciousness.
A good neuroscientist, informed by as well as informing of, philosophy, knows that MRIs don't directly measure consciousness or even close to that, and that they're not (yet) that accurate.
BUT ... a good philosopher who is informed by as well as informing of neuroscience knows that those MRIs are measuring some brain activity, brain activity happening at roughly the same time as mental activity and in parts of the brain we have tentatively identified by other research as being associated with certain types of mental activity.
So, a good philosopher of mind will welcome good scientific research that helps him or her posit further questions on the nature of mind, of consciousness and of free will, including scientific research that then helps him or her help neuroscientists.
But Hoffmann seems to fear, to some degree, actual science, not a philosophy of "scientism." He seems to fear methodological naturalism. He seems to fear a "mechanistic" take on life that undercuts its wonder and mystery.
Well, even an ascerbic existentialist phyisicist like Steven Weinberg still seems to have some degree of appreciation for some sort of magic in life, Mr. Hoffmann.
I may be overstating what I perceive his issues to be, but I don't think by too much.
Then, there are people, including some of his regular readers, who wonder why we have to specify "secular" humanism vs. just humanism.
Because, as Hoffmann notes from even a less "materialistic" era, already by the Enlightenment, non-Christian forms of humanism were arising, even if an open split was not being voiced. And, today, getting back to that neuroscience, and what it tells us about consciousness ... and things like a "soul" and its existence or likely nonexistence, Christian humanism and secular humanism will split on some metaphysical issues of major import, that in turn will affect their understanding of what issues, angles and points of view are most important within humanism.