so for your purposes, the ravings of a lunatic, the mumbled dreams of a 3 year-old and the testimony of a drunk are evidence simply because they said the words. Fine. There now can be evidence for anything so where are you, logically?
You must weigh each piece of evidence as to credibility.
You discard some. You take others under advisement and you find others to be credible.
Even if evidence is false, it is still evidence.