Here's Nigel's philosophy. It is ok for Gay and lesbian groups to discriminate against homophobes, but not ok for Christians to keep non-believers out of their groups. You can force ideology on one group but not the other. Very democratic of you.
No one is forcing ideology on anyone. If you want to be a school sanctioned group, you have to follow the non-discrimination policy. I really don't get what all the trouble is, let alone the silly ad hom bullshit.
It wouldn't be OK for gay and lesbian groups to discriminate against straight people because they're straight. It wouldn't be OK for atheist groups to keep out believers because of their religion. If you want to have a homophobe group you can go fucking nuts and do whatever the fuck you want, but you have no right to school funding of your activities.