AB,
To refute…
“Refute” means “disprove”. I don’t need to disprove claims and assertions about supposed gods – I just have to find no good reasons to take them seriously.
…what is being witnessed to,…
“Witness” is a word religious people use falsely because it reifies its object. What you should have said there was, “what is being asserted without qualification” or similar.
…you would have to proclaim the person to be a liar, or produce evidence to show they were somehow deceived.
No you wouldn’t. All you’d have to do would be to ask them to justify their claims, and when those justifications are found to be false their assertions can safely be ignored.
In addition to the recorded witnesses in the gospels,…
Which accounts fall well below even basic tests of historicity, for reasons that have been explained to you many times.
…I have encountered many people who have witnessed to their experience of God working in their lives,…
No, you have encountered many people
who have made unqualified assertions about that (see above). People from other faiths have also encountered many people who have made their own unqualified assertions about their various gods, djinns, spooks and ghoulies too.
…and there are thousands of similar written accounts throughout the history of the Christian church including the lives of the saints.
Yes, as there are in the accounts of the Norse, of the Sumerians, of the ancient Greeks, of the…
Pretty much all pre-Enlightenment societies made up stories like this to explain their satisfaction the phenomena they observed around them. Oddly (to my mind) some such remain despite the ludicrousness of their claims.
It is highly unlikely that such witnesses to the faith were making deliberate lies, so were they all being deceived?
Possibly, but the more likely explanation is that they lived in a culture in which supernatural explanations of many sorts were commonplace (some of which, like the resurrection story, had been plagiarised from previous traditions – a process called “syncretism”) and they lacked the tools and reasoning to dismiss them.