If intolerant atheists were to dominate society the result would only be an ignorant society ripe for the return of religion. Unlike religion - the freedom to think cannot be imposed on anyone. In a man believes in a different god, or even if he uses a different ritual for worshipping the same god, blind faith can decree that he should die - on the cross, at the stake, skewered on a Crusader's sword, shot in a Beirut street, or blown up in a bar in Belfast. Memes for blind faith have their own ruthless ways of propagating themselves.
Difference of opinion leads to enquiry, and enquiry to truth.
The argument is that we none of us know all truth, that the discovery of new truth is promoted by free discussion and rendered very difficult by suppression, and that, in the long run, human welfare is increased by the discovery of truth and hindered by action based on error. If there is any one thing that we humans take pride in collectively it is our ability to work together. There is a special sense of satisfaction in being part of 'a great team'. And today, in Africa, womenfolk pound their grain together, singing as they work, cementing the bonds of communal feeling and mutual support. It is adversity, however, that energizes our collective efforts in a way that nothing else can.