Not denying that most Drow are evil but the act of wearing the stone seems more to me that they just like the way it looks
Given the date on the source reference, the comment is more likely relating to the supposition (admittedly not a fair one these days), that they are lolth worshippers - within Drow society at least, Lolth worship is fairly absolute, and onxy is a stone that Lolth identifies with as well - you won't find many non-lolth worshipping drow openly wearing onxy, generally speaking.
