How much diversity is enough?

The CRE is trying to tread the line between social fragmentation and uniformity.  Meanwhile the Catholic Church wants exemption from the Equality Act because it would require Catholic child adoption agencies, contrary to their wishes, to deal with gay parents.  The same drama is being played out at more local levels: should a university-funded student society be able to choose which students to admit – for example, only those which are Christian?  Or Hindu? Or believe in a flat earth?

What principles should those who live in the same space be forced to accept?