The fallacy of ad-fidentia is committed when someone attacks the opponent’s self-confidence instead of the argument or the evidence.
Scientific method is an empirical method of acquiring knowledge, which is an iterative, cyclical process through which information is continually revised. Flat-Earthers would often question their opponents if they are 100% sure about their claims. If we admit there is a possibility we are wrong or that our claims might be revised in the future, flat-Earthers will use that to ‘prove’ us wrong.