I've only read half the thread, and now need to go and fix tea. But just to get in my ha'aporth:
This really reminds me of the thread about the Christian foster carers with the anti gay views. Cue many tabloid headlines bewailing, "Are social services going to take away the children of all Christian parents?". A couple of points which are really vital but seem to be misunderstood by many:
Short term foster carers cannot in any sense be described as 'parents' as happened a few times upthread. They are paid carers for other people's children. So we not discussing here parents' rights to have their own views and transmit them to their children. We are discussing people who have to able to sensitively handle the fact that they will be caring for vulnerable children who will come in with their own set of allegiances and values, perhaps handed on by THEIR parents.
ALL foster carers (and, to a lesser extent, adopters) have to demonstrate that they understand and can manage this. So Christian is fine; preaching homophobia is not (what is they foster children of gay parents, or gay children?). Muslim is fine, preaching holy jihad to vulnerable children is not. Being lesbian feminist is fine (to use myself as an example), telling children that their fathers are sexist pigs is not.
I am sure there are certain religious/political views that would rule you out entirely. Being BNP or in an extreme religious sect has to rule you out, because it is hard to imagine the authority could find many suitable placements for you.
It is not clear from this report whether UKIP was deemed out of bounds in principle, or whether in this particular case the couple's expression of their political views was problematic. I have to say I'm not convinced that voting UKIP is incompatible with foster care. But fervent, vocal and uncompromising allegiance to the extreme end of those views might well be.