“Much like any man can be a potential rapist, shouldn't we accept that any accuser could be a potential liar?”
Oh, most certainly! 
In fact, some insurance companies already do this: my 80+ year old MIL had a report from the fire brigade to say her washing machine must not be used, yet was told by her insurance company: “We know your sort!” 
Less for the police to investigate, too, if every accusation of theft, criminal damage, assault (by anyone on anyone), fraud etc. is regarded as a pack of lies until proven otherwise.
Or did you just mean sexual offences?