Which ones particularly annoy you? For me it's the racists, sexists and Libertarians in about that order, and particularly the assumption that these are fine positions to hold and variance from them is mind-killing.
racists, sexists and Libertarians
Slightly off topic, but I genuinely don't think I've encountered explicit sexism or racism on LW. The neo-reactionary community includes some elements of that, but they seem to be mostly on their own blogs rather than on LW itself.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
Of course, for "every Monday", the last one should have been dated July 22-28. *cough*