You shouldn't make accusations about him that you can't prove, simply put. If you can prove that he's knowingly lying to us - that is to say, that he's telling us things that he knows isn't true, not just things that you think aren't true - then it's another story. That's why screwtape requested that you not do it, I think.
There are a number of people here who are still discussing this with him. Anfauglir, for one. They're quite capable of calling him on those things without making charged accusations like calling him a liar. If you don't feel comfortable doing so, then nobody's going to make you. But you shouldn't make things difficult for the others who are trying it that way.