One of the two judges, Horacio Piombo, defended the ruling after it was publicised this week, telling Radio La Red that before Tolosa molested the victim, the child already had suffered sexual abuse at the hands of his father, "leading him to depravation."
He said that "as a result of that experience with the father, the child had showed signs of a transvestite conduct, of conduct we had to take into account".
The Argentine Federation of Lesbians, Gays, Bisexuals and Trans has demanded the judges be removed from the bench for a ruling it said placed a six-year-old victim "in the position of a suspect."
The boy's family has said it will appeal the ruling before the Supreme Court. The child's aunt told local reporters: "He raped a child and they say he's innocent because the child is gay."
Argentinian Interior Minister Florencio Randazzo, who is also running for the presidency, responded to the ruling on Twitter, describing it as "an embarrassment."
"It's repugnant to say that the presumed sexual orientation of an abused six-year-old boy is a reason to reduce the sentence of the abuser," he added.