The 68-year-old retired public servant also took umbrage at recent changes to penalty rates.
"Penalty rates are a thing that helps people, you don't cut them, I'm sorry Malcolm," Ms Lea said.
Mr Turnbull insisted the penalty rates decision had come from the Fair Work Commission.
"I'll tell you who has cut penalty rates is Bill Shorten," the prime minister responded.
That drew the ire of several other patrons who then started shouting at Mr Turnbull, with one man accusing the government of preparing to sell off the ABC.
"The ABC will be publicly owned forever," the PM tried to assure the crowd, to which one woman responded "Oh sure, like Howard said no GST!," in reference to former Liberal Prime Minister John Howard's introduction of the goods and services tax.
"You're just like [former Queensland Premier] Campbell Newman - he told lies and you're telling lies," yelled another woman.
"Ruthenberg, where's your medal?" a man yelled at Mr Ruthenberg, referring to the scandal which has dogged him for much of the campaign regarding his misidentification of a medal he was awarded during his time in the armed forces.
Mr Turnbull later played down the hostile reception in Longman, saying he believed most people "saw through Labor's lies."
"There was a lady downstairs who was obviously a strong Labor supporter and that's good I get out and meet people all over the country," he said.
The prime minister said he and Mr Ruthenberg had earlier done a walkthrough of Morayfield shopping centre and claimed he had received nothing but positive feedback, although the media had not been invited to that event.
The Longman by-election is one of five being held on Saturday across the country, with Mr Ruthenberg leading Labor incumbent Susan Lamb 51 to 49 per cent in recent polls.