I remember reading about a group at the University of Minnesota when I worked there. All student groups must sign a contract saying that they do not discriminate in membership based on gender, religion, race, sexual orientation, etc.
http://www.mndaily.com/articles/2003/11/05/7299
The Christian Maranathas, always using something to grandstand, said that they refused to sign, because that would mean that they would have to allow membership of those that were contrary to the faith - namely, gay people. They didn't want a gay person trying to be one of their leaders, and because it was against their belief.
In response, students responded negatively. One said, "If you are going to receive student funds for your organization, you can't discriminate against students. You can't take money from some of the gay students, then refuse them access to your group that they helped to contribute to.
However, every other group signed the contract. Are University Republicans afraid of liberals infiltrating and trying to bring down their organization, or change their beliefs? Are vegetarians afraid of meat eaters becoming leaders?
There seems to be in conservative christians, such as Maranatha, a suggestion that they are protecting themselves, but which rings much clearer as fear - and often, imagined fear.
Maranatha has to use gimmick (Quote the 10 commandments and win a candy bar) to draw anyone to their table. Most of the time, the people that they draw are those who simply want to argue, but few are running to join their group. They have a really bad rep on campus. A christian, when I went there in the 80s, told me that it was closer to a cult, and to watch out for them.
If this forum was used to only allow the postings of those that agreed with the church (if they could ever agree on anything), it would be a really boring forum. No one would dare question, no one would be forced to think, to consider if their understanding is wrong, etc. Jesus was always confounding his disciples by doing things that were clearly out of their understanding.
In the parable of the Good Samaritan (which people think of as a person that does something good), two holy men pass the beaten man. The Samaritan, who were considered a step down from the tax collectors and prostitutes, helped the man. And often, being showed that the one who showed mercy was following God, and not the one who simply appeared to follow God, (the holy men), it often shocked those that listened to him.
Diversity. Even Jesus brought that to people to give them better understanding.