Read Chapter 4. It is extremely important to separate your evaluation of an argument from your prior belief about the truth of its conclusion. A common mistake is to ignore the argument and go directly to contesting the conclusion. If you are unwilling to accept the conclusion of an argument, you should have reason to reject at least one of the premises, or the reasoning from the premises to the conclusion, or both. To criticize an argument merely on the grounds that you disagree with the conclusion is not an adequate response.
Good people do suffer as a result of natural disasters.
Therefore, A benevolent and all-powerful god does not exist. Thus it is impossible for a valid argument to have premises that are all true and a false conclusion. Doug is a man. Therefore, Doug is mortal. In order to be valid, an argument doesn't necessarily have to have true premises.