Former Marist College Canberra student Damian De Marco says he was not surprised a lawyer for the order had used his past drug use to question his testimony.
Mr De Marco said that "given their sociopathic disregard of the welfare of the victims I wouldn't have expected much less".
Mr De Marco returned to the stand on Wednesday morning at the sitting of the Royal Commission into Institutional Responses to Child Sexual Abuse in Canberra.
He was closely questioned by Marist Brothers' advocate Peter Gray over his statements that his complaints about Brother Kostka Chute in 1986 and 1993 had effectively been ignored by the Marist Brothers.
Mr De Marco said he had spoken to his housemaster John Doyle in 1986 and Marist Brothers provincial Brother Alexis Turton, in 1993.
Mr Gray put it to Mr De Marco he may not have spoken to Mr Doyle but another teacher.
Mr De Marco denied this.
Mr Gray also put it to Mr De Marco that when he told Brother Turton of an assault on him by Brother Kostka Chute in 1981 he said it had not been significant.
"I would not have gone to the provincial to tell him I had been hugged," Mr De Marco said.
"I regarded it [Kostka's action] as a sexual assault on me.
"I communicated to him, in words I cannot exactly recall, that I had been assaulted by Brother Kostka."
Justice Jennifer Coate told the hearing the report on which Mr Gray was basing his statements of drug use by Mr De Marco indicated he had sustained no cognitive impairment.
Mr De Marco said his experiences had been a factor in his marijuana use.
John Doyle was expected to give evidence on Wednesday.
Terrence Heinrich, the then Marist College Canberra headmaster, will also be appearing before the commission.