Edmund Burke once said:
Boldness formerly was not the character of Atheists as such. They were even of a character nearly the reverse; they were formerly like the old Epicureans, rather an unenterprising race. But of late they are grown active, designing, turbulent, and seditious.
Secular Americans can run for office and adequately represent theists, just as theists in office can represent their secular constituents proudly and openly.
But I have my doubts as to whether the organizers of this rally really mean it. One of the principal sponsors is the Freedom From Religion Foundation, which is actively hostile to religion.