'When did we change from presumption of innocence to presumption of guilt?' - Because in some locations the police etc are not allowed to disbelieve an complainant and must act upon the accusation.
Add to that and the lack of anonymity for people accused of rape and your in a situation where an accusation alone will loose you your job and with the publicity you'll not be able to find another role in order to pay lawyer fees to help defend yourself.
Don't believe its true, well the first part I saw happen to a ex-colleague who basically took a plea bargain because he could not afford to fight it especially as he couldn't afford parole. The second one I've seen has now got a court date which is 3.5 years from the start of the investigation and >2 years since they got charged.