Adam,
On no expert of this but I'm currently trying to educate our committee and also politely upset people for a living (and that isn't just me being flippant) so I do have a grasp of delivering news which most won't want to hear.
Firstly, deal in what you are quite happy to present as facts, i.e. this is good architect because of this, that and the other. Be sure to explain it as being universally accepted within architectural circles and not simply a matter of opinion. If you let the necessary work become perceived as simply a different viewpoint (and that it exactly what people will automatically see it as because they have no idea how little they know and it'll help their cause to make the whole thing as cloudy as possible), the facts as you see them will simply be dismissed. Most people are smart enough to realise when there's an educated view and an uneducated one and they hate the idea of being left in the dumb camp. Do however throw them the odd bone, if only to emphasise that everything else you are promoting is fact.
I've personally gone down the route, and since found that it's a route employed by Tom Doak, that you should draw on the support of the great architects. Don't be afraid to literally bring quotes to the table from the likes of Mackenzie. In doing so you make it a debate not between you and others but between the greatest architects in the history of the game and your fellow members. Essentially, politely ask them if they really think they know better than the people that wrote the books in front of them.
Remember in all of this that getting the message across to everyone is crucial. You can't expect people to adopt your viewpoint if your viewpoint doesn't get beyond the committee. If you have a newsletter, write an explanation within. Also email all members with an explanation. Be available to answer questions and be prepared to stand strong. Some people are going to come at you convinced that they are right and you are wrong. Let them rant until they wear themselves out and bring them back to Earth with your facts. Some people will love you for educating them and some certainly won't. Just remember that most people instinctively fear change and are only going to 'get it' when it's all done and dusted, and only then gradually.
And finally, the very best of luck!