"After Hoover" meaning Herbert or J. Edgar? Becuase the latter was at the BI and FBI from 1924 to 1972. 1972 to 1990 is a small window there.
Ask George Takei about detention without trial. Look up US Executive Order 9835. Read up on Dennis v. United States if you don't believe the US curtailed civil liberties. Read up on the Hollywood blacklist. It wasn't just McCarthy and Hoover with some two-man mission.
Ask the folks at Kent State who were shot for peacefully protesting the Cambodian campaign in 1970, just before your window opens. Read up on Ruby Ridge. That's just after your window closes.
So you're basically asking "when, during this 18 year period, did we ever have curtailed rights?"?