This sides more with you on whether the seminaries were opened to gays in the 60s and 70s or if they were always open to gays.
When priests who abused minors are grouped by the
decade of their ordination to the priesthood, each
group displays a distinct pattern of behavior. The
social influences can be seen in the behavior of each
ordination group, or “cohort.” Men ordained in the
1930s, 1940s, and 1950s did not generally abuse before
the 1960s or 1970s. Men ordained in the 1960s and
the early 1970s engaged in abusive behavior much
more quickly after their entrance into ministry.
•
The ordination cohorts of men entering the priest-
hood before 1960, and before any moderation of the
regimentation of seminary life, represent 44 percent of
those later accused of abuse.
•
There was no evidence of any significant level of sex-
ual activity among seminarians before the mid-1970s.
The men ordained after 1975 had a lower level of sub-
sequent abuse.
usccb.org/issues-and-action/child-and-youth-protection/upload/The-Causes-and-Context-of-Sexual-Abuse-of-Minors-by-Catholic-Priests-in-the-United-States-1950-2010.pdf