I would put a lot of that down to the individual as much as the drug. I think that those who act irrationally violent or paranoid on the drugs tend to be the less stable ones off the drugs. Yeah the drugs may have tipped them over the edge or created a scenario for them to act on their irrational impulses which would have otherwise not have happened if the drug didnt exist but in most cases i would lay blame with the user rather than the drugs.
The addicts the media love to label as criminals eg. desperate thieves or violent people, likely are not top blokes with or without the drugs and likely something wrong in their life caused them to use drugs as a social/emotional/mental crutch to cope with something or other. I agree some people can act out of character but it wouldnt surprise me if convicted addicts have offences that were committed off substances.
Decriminalising certain drugs removes the stigma involved and makes it easier to target the real issue why some people end up relying on drugs, rather than just slapping a 'druggie' name badge on anyone that acts outside the norm and declaring the reason for any misbehaviour 'drugs'. I bet by de-criminalising some drugs you end up reducing the number of major issues you get with drug addicts, despite the number of takers increasing.
That said, i dont think the UKs current binge mentality suits decriminalisation just yet...
Those guys who go out to clubs on a Friday looking for a fight after a few drinks are likely still knobs during the day and when sober. They may not get into as many fights but i would still lay 100% of the blame on the blokes.
Yes, but they're now knobs high on drugs - legally.