The battleground is YouTube and Scientology's weapon is a clip of me losing it in the "Mind Control" section of a gruesome exhibition.
Scientology has fought many battles to keep its secrets off the web, now they are using it to attack my investigation into them.
Scientology has prepared an attack video, and they have shown the Scientology v Sweeney shouting match to anyone who would watch it.
There is talk of 100,000 copies being released.
Scientology works. That is the message from celebs like John Travolta and Tom Cruise - who is, some say, keen on recruiting new Hollywood arrivals David and Victoria Beckham to what he calls his religion.
Others back the Church in various ways: Chief Superintendent Kevin Hurley of the City of London police helped open a new £20 million Scientology centre in London, and the authorities in the City of London have granted it cut-price rates.
If you are interested in becoming a TV journalist, it is a fine example of how not to do it. I look like an exploding tomato and shout like a jet engine ... it makes me cringe
But start asking questions and you see a different face of Scientology.
While making our BBC Panorama film "Scientology and Me" I have been shouted at, spied on, had my hotel invaded at midnight, denounced as a "bigot" by star Scientologists and been chased round the streets of Los Angeles by sinister strangers.
Back in Britain strangers have called on my neighbours, my mother-in-law's house and someone spied on my wedding and fled the moment he was challenged.
I have met mothers who say they have suffered Scientology "disconnects" - meaning that their children have cut them completely out of their life so that they can spend more time with an organisation which a judge in 1984 characterised as "corrupt, sinister and dangerous".
Scientology has two faces - nice and smiley, and sinister and dark. If you do not believe me, go and see their exhibition in Los Angeles, Psychiatry: Industry of Death. You enter through a door that is a mock-up of a torture chamber.
Scientologists want "the global obliteration" of psychiatrists, who they say were to blame for the rise of Nazi Germany.
To prove their point, they showed me hideous images of people having needles stuffed in their eyeballs, of patients undergoing electric shocks and having their brains operated on.
Sickening, nasty and wholly unconvincing - modern psychiatry, for all its faults, is not Nazi and to press the point in the way that Scientology does devalues the horror of the Holocaust.
Ironically or not, it was in the "Mind Control" section of the exhibition that I lost it.
As often in life, I snapped over something completely different and quite trivial.
Top Scientologist Tommy "Don't mention the word cult" Davis had been goading me all week, and on the seventh day I fell into his elephant trap. He shouted at me and I shouted back, louder.
L Ron Hubbard wrote the founding texts of Scientology
If you are interested in becoming a TV journalist, it is a fine example of how not to do it. I look like an exploding tomato and shout like a jet engine and every time I see it makes me cringe.
I apologised almost immediately, Tommy carried on as if nothing had happened but meanwhile Scientology had rushed off copies of me losing it to my boss, my boss's boss and my boss's boss's boss, the Director-General of the BBC.
I lost my voice, but not my mind.
This is the context Scientology will not tell you about. I have met too many good people who say Scientology was founded by a liar, L Ron Hubbard; that it attacks its critics without mercy; and the celebrities who endorse it have not the foggiest idea what it is really like.
Take "Rosemary", who is an ordinary mum and lives in England. She had two children and one died. Her surviving daughter was also her best friend. Then her daughter joined Scientology and her mother saw less and less of her.
Almost two years ago she received a "disconnect" - a letter cutting her mother out of her life totally.
Rosemary received no Christmas cards, no birthday cards, no Mother's Day cards.
Rosemary said Scientology was a cult. It was one of the most moving and shocking interviews I have ever done.
Out of the blue, three hours after we left, her daughter came round for the first time in almost two years seeking a reconciliation. The next day she begged her mum not to use the interview. So we won't.
Pay as you go
In Florida I met Mike Henderson, who with his wife Donna Shannon, spent $1m over three decades on Scientology's path to superhuman powers. When the couple left, they were disconnected from 20-odd family members left inside Scientology.
Mike's father - also disconnected - is dying, but five out of his six children will not speak to him because they are still inside Scientology.
John Sweeney spent many weeks investigating Scientology
After a long day with Mike and Donna we went back to our hotel at midnight, only to find Tommy Davis waiting in the lobby with his own black-clad Scientology cameraman.
He harangued me for talking to the heretics. I told him that Scientology had been spying on the BBC and that was creepy.
In LA, the moment our hire car left the airport we realised we were being followed by two cars.
In our hotel a weird stranger spent every breakfast listening to us. In all, we count 13 strangers - private investigators? - who were following us. Scientology denied sending PIs after the BBC.
Scientology is a pay-as-you-go religion - which is one of the reasons why the Charity Commission in Britain does not class it as a religion.
When you have paid as much as £100,000, you get to Operating Thetan Level Three and learn about "The Incident".
L Ron wrote that 75 million years ago an intergalactic space alien lord called Xenu kidnapped Thetans to earth, dumped them in volcanoes and blew them up with atomic bombs.
Ex-Scientologists have insisted to me that Xenu is part of Scientology. If so, it is a religion that requires its followers not to tell others about its core belief, which is very odd.
Critics say that if we all knew about Xenu, then Scientology could not charge people as much as £100,000 to find out about him.
Despite all the pressure - the letters from lawyers, the letters from MPs, the strangers knocking up my family and neighbours - if people from "disconnected" families tell me that Scientology is a cult, that will be reported.
Scientology And Me, Panorama, Monday, 8.30pm, BBC1.