My interpretation is that he provided enough evidence to the RCMP that convinced them to stay the case, since they likely thought the evidence they had to convict Barker was weak. This lead to him not having a chance in court to clear his name.
Had he not spoken to the police at all, and instead waited to present his evidence in court, he likely would have been found not guilty and therefore would have cleared his name.
Him talking to police worsened the situation because they are not the ones who evaluate the evidence and make a conviction decision (judges/juries do that). The job of the police is to collect evidence, and Barker did that for them (to his detriment).
Had he not spoken to the police at all, and instead waited to present his evidence in court, he likely would have been found not guilty and therefore would have cleared his name.
Him talking to police worsened the situation because they are not the ones who evaluate the evidence and make a conviction decision (judges/juries do that). The job of the police is to collect evidence, and Barker did that for them (to his detriment).