1975 – Canada 81% of inmates involved in aggressive incidents had taken diazepam (Valium) and 3.6 times as many acts of aggression occurred in inmates while on these drugs. Full Text
1978 – Utah A high level of riots, stabbings, cuttings, murders, self mutilation attempted suicide were attributed, at least in part to high consumption of benzodiazepines in a Utah State prison. Full Text
1995 – New South Wales, Australia Restriction of clonazepam (a benzodiazepine) prescription was implemented by the Corrections Health Service of New South Wales due to it causing emotionally reactive and aggressive behaviour with self-harm and suicide attempts in inmates. Full Text
1995 – Parkhurst, UK Tranquilliser prescription (mostly benzodiazepines) was reduced from 3.5kgs p.a. in 1990/91, to 0.15kgs in 1994/95. Correspondingly physical assaults by inmates on another person reduced from 5 in 1990 to 0 in 1995. Full Text
I see an argument against it.. It doesn't take a genius to find it, either.
(There's loads more but.. Just search for: benzodiazepines and aggression / depression)