Hesitant to wade in but...If you want to take my comment out of context, that's entirely within your rights.
Yes, there is a difference between a post and a person as well as speech and a person. Posts and speech expresses ideas that anyone can disagree with. Otherwise, what's the point of these forums? However, aside from disagreeing with the tenor and content of his/her post, I'm not judging the poster in any way.
I think @Canuck is saying that if you say the comment is "witless", you're implying that the author has no wit. I think you're saying "the author was not using his/her wit when posting it, whether or not he/she has wit". There's a fine distinction, if I'm understanding correctly.