To be honest, I don't see such clash. What I do see though are ontological mistakes stemming from incomplete views resulting in humanism turned into an anthropocentric rule order not that dissimilar from theistic views and scientific rendering of universe as merely a ruthless meat grinder, which is, again, in the vein of theistic denigration of all things material.

I mean, humanism as non-theistic "ethical life stance, which affirms that human beings have the right and responsibility to give meaning and shape to their own lives [, which] stands for the building of a more humane society through an ethic based on human and other natural values in the spirit of reason and free inquiry through human capabilities," does not clash with scientific observations in any way. In fact, they go hand in hand. And what's more, those stances and views are fully compatible with ancient traditions, which, with each passing day, I'm more and more reluctant to even consider theistic at their core (and some, such as Taoism or Buddhism, are, indeed, non-theistic).