The man, who was dating the child's mother, was babysitting when the assault happened in Pointe-aux-Trembles.
The Crown had requested a six-year prison term for Boiré-Dubé who left a 2.5-centimetre tear in the boy's anus that had to be surgically repaired.
"Can you think of a more vulnerable victim than a 2 1/2-year-old child who cannot make a formal complaint?" prosecutor Anne-Andree Charette asked at a pre-sentencing hearing in Quebec Court in December last year. "All he could say was, 'Boo boo, boo boo.' "
Boire-Dubé still denies the essential elements of the assault, which took place in November 2002 while the child's mother was at school.
A pre-sentencing report painted Boire-Dubé as having narcissistic traits, anger management problems and a controlling personality. It indicated he may even eroticize violence.
The report lamented that Boire-Dubé didn't co-operate fully, clamming up about details of his past - including a four-year stay in a group home.
"All this leads the experts to conclude they cannot exclude the possibility he has pedophiliac tendencies," Charette said.
Boire-Dubé has always maintained all he did was insert a suppository into the constipated boy a little too brusquely.
The court rejected his explanation after a child abuse expert said only a vibrator, erect ***** or other large object could have caused such injury to the boy.
But Boire-Dubé's lawyer said it's unfair to fault his client for maintaining his innocence.