In some ways, being against theocracy could be bad. If the religion in general was benevolent, had members who practiced that benevolence in all aspects of their life, and were moral, ethical, and upstanding people, then there would probably be a big call for them to be enshrined in the government. If they were competent administrators and applied the principles of their religion to their work, for the improvement of all people under their eye, then most people probably wouldn’t have problems with keeping them in government and letting them rule by religious principles.
Where the problems start are in implementation and in our various dispositions as human beings. For various reasons, some people just tick us off, or we’re taught in one way or another that some people aren’t as good as we are, because they lack something, be it fairness of skin, affluence, or the big one, religion and the “salvation” and “morality” that goes along with it. A lot of the influential writers, founders, and figures of religions recognized that this happened, and have teachings that instruct their followers not to do it. The Prophet spoke of the People of the Book, those who weren’t Muslim but worshipped the same G-d. Samaritans, tax collectors, “sinners”, Romans, Gentiles, the poor, and women are all part of the story of Jesus of Nazareth. The message is pretty clear: These people are worthy, too. The rain falls on the just and the unjust. G-d does not play favorites, but he rewards those who do what he instructs and calls them his chosen people.
The Founding Fathers recognized this, too, and thus enshrined into the Constitution a prohibition against adopting a single religion or excluding other religions from being able to practice. They wanted to get rid of the possibility that our own human biases would lead us to systematic exclusions of people based on their beliefs.
Right now, much of the world thinks they are G-d’s chosen people by virtue of the place they were born, the family they were born into, or the religion they follow. And they think they should shout from the rooftops about their special status. They expect to be obeyed, to be given special treatment, to have their view enshrined in the laws of the land, because G-d demands it of his people. Jesus had words about them, too.
“And whenever you pray, do not be like the hypocrites; for they love to stand and pray in the synagogues and at the street corners, so that they may be seen by others. Truly I tell you, they have received their reward.” (Matthew 6:5, NSRV)
“When you are invited by someone to a wedding banquet, do not sit down at the place of honor, in case someone more distinguished than you has been invited by the host, and the host who invited both of you may come and say to you, ‘Give this person your place’, and then in disgrace you would start to take the lowest place. But when you are invited, go and sit down at the lowest place, so that wen your host comes, he may say to you, ‘Friend, move up higher’; then you will be honored in the presence of all who sit at the table with you. For all those who exalt themselves will be humbled, and those who humble themselves will be exalted.” (Luke, 14:7-11, NSRV)
People are telling the world about their religion every moment of every day of their life. Pat Robertson, Jerry Falwell, Fred Phelps, George H.W. Bush, Mahmoud Ahmadinejad, King Abdullah, the barista at Starbucks, the preacher on the street, the vested priest celebrating the resurrection festival, the hooded priestess celebrating the coming of spring. The person that says homosexuals go to hell, and the person that defends the right of homosexuals to be married. Everyone says “This is what an X is”, whether religious or not, in everything they say and do. Some people are much more subtle about it than others, and some are much more in tune with the teachings of their founders than others.
So, I suppose my parting question is just this - which would be more in tune with being a good member of your religion - enshrining it into law and forcing people to worship the same way you do, making loud and public proclamations of your faith (under penalty of imprisonment or death if you don’t), and displaying your faith as conspicuously as possible to everyone, or by doing works that bring about a better quality of life for everyone, regardless of faith?
“But whenever you go pray, go into your room and shut the door and pray to your Father who is in secret; and your Father who sees in secret will reward you.” (Matthew 6:6, NSRV)