I do think you look too critically at people who have had problems in the past.
Like I consider myself a nice guy and good friend but even I have done drugs when I was young and stupid. As it happens I have a caution for possession of marijuana and a caution for theft (even though I was an unknowing accomplice I still got done (similair to unknown possesion of stolen goods - what a silly law that is)) yet now aged 26 I can honestly say I am one of the nicest and mature people I know...