If Dawkins had said something like:You show me science text books which the laws of physics speaks of meaning for the universe. Dawkins is merely attempting to avoid the anthropomorphic trap in order to BE scientific.
"the laws of physics, chemistry and biology have nothing to say, one way or the other, about values such as good and evil."
then I think you'd be right. But he doesn't seem to be saying that. In the quote from the OP he doesn't seem to be asserting the value-neutral character of physical sciences. He seems to be saying that they actively preclude the existence of certain values:
"The universe we observe has precisely the properties we should expect if there is, at bottom, no design, no purpose, no evil, no good, nothing but blind, pitiless indifference."
That's why I agree with the proposition that the above is more polemic than science. It's not a dispassionate attempt at neutral observation. I don't know if it was supposed to be.
-- Updated Mon Jul 17, 2017 12:04 pm to add the following --
On the other hand:
Perhaps Dawkins' use of the phrase "at bottom" is key here. He isn't ruling out the existence of morality in the creatures that inhabit the universe, such as us. He's just saying that observations of the large-scale universe suggest that there is nothing recognisable as morality in its underlying structure or physical laws. He doesn't rule out morality as an emergent property of a pitiless, amoral universe.