How to use a fake blog to accuse someone of anything

I can change anything in an old blog entry as long as it exists, and use it against anyone I deem fit, as long as there is no alibi for the accused. That includes accusations of attempted murder, rape, paedophilia, robbery, harassment, violent behaviour and the like. That person will probably have to deal with a lot of crap such as going to court at their inconvenience. Even if I can't I can always do this in secret and use it later for false allegations of crime.

Simply said, blog entries can simply be abused for personal vendetta and should not be admissable in court.