Has his post offended you or something? You employ pretty strong language, and "this post makes me less interested in inviting you over for dinner again" is a kinda public way of breaking off a friendship, which (regardless of cause) is somewhat socially humiliating for the person on the receiving end. Is that really necessary? Settle such personal details via PM?

I don't see it as a sort of grey fallacy argument to note that "lying" isn't much of a binary property (i.e., either you lie, or you don't). There may be simple enough definitions on the surface level, but when considering our various facets of personality, playing different roles to different people in different social settings, context-sensitivity and so on and so forth, insisting on anything remotely like being able to clearly (or at all) and reliably distinguish between "omitting a truth" and "explicitly lying" versus "telling the truth" loses its tenability. There are just too many confounders; nuances of framing, word choice, blurred lines between honesty and courtesy, the list goes on.

Yes, there are cases in which you can clearly think to yourself that "saying this or that would be a lie", but I see those as fringe cases. Consider your in-laws asking you whether the soup is too salty. Or advertising. Or your boss asking you how you like your new office. Or telling a child about some natural phenomenon. The whole concept on Wittgenstein's ladder ("lies to children") would be simplistically denounced as "lying" in an absolute framework.

"Hair trigger about mere true facts" is disregarding all these shades of "lies" (disparity between internal beliefs and stated beliefs), there are few statements outside of stating mathematical facts for which a total, congruent correspondence between "what I actually believe" and "what I state to believe" can be asserted. Simply because it's actually extremely hard to express a belief accurately.

Consider you were asked in a public setting whether you've ever fantasized about killing someone. Asked in an insistent manner. Dodge this!