Abdul Majid Qazizada, 51, had argued that Ramadan was a time when Muslim men "don't even touch their wives".
He was yesterday found guilty of the aggravated indecent assault of a 23-year-old woman who suffers cerebral palsy and epilepsy.
Magistrate Jennifer Betts said Qazizada claimed he was a devout Muslim who was fasting when the attack occurred in September last year.
" 'Men don't even touch their wives (during Ramadan)', were his words," Ms Betts said in Ryde Local Court.
The court heard how the woman got into Qazizada's taxi to go home after going out with friends at Ryde-Eastwood Leagues Club.
During the short ride home, she felt at first "a little scared", then later "very worried", when Qazizada repeatedly told her: "You're a lovely lady." After parking in the driveway of her home, Qazizada told the woman he would help her get out of the taxi.
Throughout the assault, he asked the woman: "Are you all right?". Each time she replied: "No."
Qazizada eventually left, saying: "Have a good night."
The woman immediately went to her neighbour's home to report the attack.
The court heard that the woman uses a walking frame to walk short distances, a wheelchair to travel long distances and suffers weakness to the left side of her body.
Outside court his victim, who cannot be identified, told The Daily Telegraph she was happy to see her attacker brought to justice.
"It's been a tough time for me and my family. I feel good about what's happened today," she said.
Qazizada was granted bail pending sentencing on December 9.