The practice, in this case, is known as scare quoting. Scare quotes are used very often as a substitute for constantly writing soi disant or "so-called". This is different from use-mention quotation, which is to indicate that one is citing the word in question instead of simply using it, and different from reference quoting, in which one purports to present exact words from another source. Thus, when one sees "mainstream" masonry to refer to those USA masonic organizations that are not PHA and have been traditionally white or predominantly white, this is a substitute for "so-called mainstream". PHA masonry is in truth no more mainstream than the "mainstream", but the term has been applied so long that it is a convenient short-hand.