Nothing is Certain

Below are the questions that come to my mind while reading Bahnsen's critique of Bertrand Russell's intellectual position:

If nothing is certain, how can you be certain that God does not really exist? If nothing is certain, why are you arguing that Christianity is false and human autonomy is true? If nothing is certain, is there meaning in arguing against the belief of another? 

If nothing is certain, how can you say that Jesus is inferior to both Socrates and Buddha?  If nothing is certain, how come you are so sure that Christianity is the primary obstacle to the moral progress of humanity? If nothing is certain, how can you say that progress is even possible? On what basis are you saying all of these? 

Do you have any objective moral standard to make your personal judgment of Christianity? If none, but your own, then anyone on the basis of your intellectual system has the right to dismiss your moral judgment as anything but certain.