Four years ago, Louis Theroux visited the homophobic Christian extremists of Westboro Baptist Church (the Phelps ‘family’), and the UK viewing public was treated to the sight of a bunch of crazy Americans picketing soldiers’ funerals, shouting about ‘fags’ and teaching their kids how to hate. Four years on, it’s pretty much the same, except that there have been a lot of defections, and they now take great pleasure in calling Obama out as The Antichrist. Lovely people, all of ‘em.

It’s easy for us to judge these people as ignorant, ill-educated bigots. Because they are. But Louis largely retains his trademark calm and even demeanour when dealing with, say, an eleven-year-old child prattling on about original sin, or a recent convert to the church equating Theroux’s ‘power’ and iniquity to that of Pontius Pilate.

Louis visits a family whose daughter, Lauren, left the church soon after the original documentary. Lauren’s parents have removed all photographs of her from their home, something Louis points out, only to be called “a jackweasel”, which is nice. He then visits Lauren, who appears to be living the normal life of a young, free, single gal (that is, one FULL OF SIN), and who tells the real story of her banishment - she had been chatting online with a boy, and the church chucked her out. Given her bizarre upbringing, Lauren seems incredibly well adjusted, remarking “some people lose their parents to cancer...I lost mine to a cult” Later we will meet Libby, who was banished for wearing a bikini on holiday.

Four years ago, the Westboro lot mainly picketed soldiers’ funerals, but nowadays they tour the whole country, looking for people to offend. We see them protesting outside a college campus, where a play about homophobic hate crime has angered them. Weird, creepy and extremist, they may be, but one church member’s imaginative reworking of Lady Gaga’s Telephone, damning the gays because they “love fornicating, f-fornicating” is nothing if not inspired.

Eleven year old Noah has a freakishly tidy bedroom, and talks at length about “filthy fags” and “The Antichrist Obama”, and our hearts genuinely go out to him, because it’s not right for a child to be subjected to these overt messages of hate and intolerance. Eighteen year old Grace has four chaperones supervising her conversation with Louis, because she doesn’t trust him not to entrap her using her own words, which certainly seems like a normal and in no way slightly mad concern. Grace is actually quite an accomplished photographer, and that makes us a bit sad, for about two seconds, because then Grace’s chaperone Taylor starts talking about how they “righteously” BURNED A QUOR’AN, and we sort of went a bit deaf from anger.

Four years on, Louis Theroux has succeeded in creating a documentary as compelling, repellent and eye-opening as his first visit to Westboro. It’s genuinely a bit terrifying, and to be honest, if we’re going to go to Hell for f-fornicating, bring it on. Better, surely, than being stuck in their a Heaven, full of bigots and homophobes.

Louis Theroux- America’s Most Hated Family in Crisis is available to watch on the iPlayer, or “The Beeb on the Internet on demand”, as our Mum-in-law calls it.