I think it is all about PROOF. If you can prove absolutely that people have Lied, and that the lie, had it been believed, would have cost someone 25 years, then yes, I think it harsh but just to give a false accuser that same sentence.
But I fear that in many cases it is word against word, and how do you find the truth then? I am certainly not in faviour of a rapist getting off either. No one is, I think. And you cannot punish the accuser simply because you could not prove the case. They are too hard to prove for that.