Perhaps quietly disbelieving someone or even better, sending a private message to the person in question (if that facility is available.) to attempt to ascertain where they got their info from rather than feeling the need to shout LIAR or something similar to anyone who will listen is the better course to take. Even people who have got things wrong in the past, may have a range of different connections to the club so it does not follow that they are automatically wrong. I have known of a few cases of that on here and through being smart have managed to gain quite a lot of information about the goings on at SFC. This forum really is an interesting place to find information if you are a bit more open minded and not so quick to shout people down without knowing if they are telling the truth or not.
I call my approach the "Trousers" policy by the way. Never dismiss someone no matter how outlandish their claims