There's an interesting discussion of the veracity of that 'source' here:
https://history.stackexchange.com/questions/8090/did-gorbachev-say-that-his-intention-was-to-destroy-communism
The usual rules of scepticism apply: the more extraordinary the claim, the more extraordinarily compelling the evidence for it needs to be before it should be accepted. And the evidence for this extraordinary 'confession' seems a little thin.