Noisy Believers

Nietzsche said 'To him who feels himself preordained to contemplation and not to belief, all believers are too noisy and obtrusive; he guards against them.' And this aphorism came to my mind again and again today, as i was being forced unwillingly into an argument on religion. Why do these religious people consider it their duty to convince others of the validity of their beliefs, and anything short of a full acceptance is seen an insult to their faith. This is very irritating. Believers are too noisy even when they are silent!