This topic seems to get brought up 2-3 times a year. As far as I've been aware, Squeen's kinda taken a "don't-ask-don't-tell" stance, so I don't really see the problem with 3rd party tools if they enable players to enjoy the game more and they aren't using the tools as a source for harassment.
I just also know that some players, who haven't had done any research or had experience with 3rd party add-ons, immediately associate such things to parsers and naughty mods, or they think such players are doing something to their game client. There's bound to be some discomfort around the idea as a result.