When police arrived 12 women and children moved off after being spoken to by the officers. No one was arrested for the damage.
Mr Armstrong told how he was watching television with two of his sons when he heard people from neighbouring streets chanting "paedophile" outside.
He had to go outside and show them his passport and driving licence to prove they had got the wrong man.
'Irresponsible reaction'
He said: "They were saying 'Here he is, here he comes' and the policeman was saying it's not who you think it is.
"So I looked at them and said 'I have got three kids of my own. I don't want one of them living near me same as you don't.'"
Assistant Chief Constable Alan Green said the incident, which happened at 9pm in the Beswick area of Greater Manchester was an "irresponsible reaction of emotive stories in a national newspaper".
But News of the World editor Rebekah Wade said the newspaper's campaign to name and shame more of the UK's 110,000 convicted child abusers would continue, despite widespread criticism from ministers, police chiefs, probation officers and other experts.
Murdered schoolgirl Sarah Payne's parents Michael and Sara also repeated their backing for the campaign, saying it would protect youngsters.
'Overwhelming public support'
Ms Wade said the News of the World did not condone vigilante attacks but "every parent has an absolute right to know if they have a convicted child offender living in their neighbourhood".
She said: "The disturbing truth is that the authorities are failing to properly monitor the activities of paedophiles in the community.
"The continued support of Sarah's family for our campaign plus the
overwhelming public support means that the News of the World will continue it's long tradition of exposing and investigating those who are a danger to our society."