I cannot know for certain but I think God is very improbable, and I live my life on the assumption that he is not there.
Dawkins accepts that one cannot know for certain that God does not exist, after all, this is an empirical claim and all empirical claims carry some degree of uncertainty. However he reckons that the likelyhood that God exists is so very slim, due to the lack of empirical evidence, that he lives under the assumption that such a being does not exist.
The God of the Old Testament is arguably the most unpleasant character in all fiction: jealous and proud of it; a petty, unjust, unforgiving control-freak; a vindictive, bloodthirsty ethnic cleanser; a misogynistic, homophobic, racist, infanticidal, genocidal, filicidal, pestilential, megalomaniacal, sadomasochistic, capriciously malevolent bully.
In the opening sentence of chapter 2, Dawkins uses a long list of words associated with prejudice to describe the God of the Old Testament, while also consigning him to the realm of "fiction". This, combined with the rich vocabularly, has an emphatic effect, truly emphasising the supposed evil of the a figure so many worship. It is for this reason that this quote is arguably one of Dawkins most famous (and for many, infamous).
Do you really mean to tell me the only reason you try to be good is to gain God's approval and reward, or to avoid his disapproval and punishment? That's not morality, that's just sucking up, apple-polishing, looking over your shoulder at the great surveillance camera in the sky, or the still small wiretap inside your head, monitoring your every move, even your every base thought.
Dawkins uses a rhetorical question to emphasise what he sees as the ridiculousness of claiming the only reason one should try and be good is to gain the approval of a hypothesised divine being. He attempts to illustrate this absurdity with the analogy of "the great surveillance camera in the sky", presenting God as an intrusive force as opposed to a moral one.
Faith can be very very dangerous, and deliberately to implant it into the vulnerable mind of an innocent child is a grievous wrong.
The repetition of very emphasises Dawkins sincerity to this matter of child indoctrination, one can infer from the quote that he sees it almost as a form of abuse. The emphasis of the "innocence" and "vulnerability" of the child appeals to the empathy reader, which - with the addition of the value statement at the end of the sentence ("greivous wrong") - acts as a moral statement that demands a reform of the status quo.
Do not indoctrinate your children. Teach them how to think for themselves, how to evaluate evidence, and how to disagree with you.
The short emphatic sentence "do not indoctrinate your children" delivers Dawkins message succintly, arguing that children should be free from the teachings of faith when growing up. This is followed by the imperative "teach" them, as he attempts to command the reader to change their actions. The rule of three is used through the repetition of "how to" adding to Dawkin's instructional message. As religious faith is typically sustained through the passing on of religion from parents to children, Dawkins seeks a change in the system which would arguably result in the gradual demolition of the supposed "God Delusion" altogether.
