GREAT letter! To the point, and not a wordy theological argument. One thing the spell checker might not catch is the "to many" at the bottom of the second paragraph: should be "to
o many" (two o's).
I like the thoughts, but in my opinion - and this is just my take on the situation. These guys are probably hit all the time by "apostates". As soon as you mention their false teachings, you may lose your audience. "Oh, another misguided apostate, blah, blah, blah, file this one away".
But, you have some good points about how they hurt people. If the guys reading this have any heart, it may touch them, make them feel guilty for how they've handled their flock. (Probably more at the local level than the society).
If you leave out the "wrong teachings" stuff and stick to the other ways they've hurt people, they may read it all the way through without dismissing it.
That's just my opinion. There's something great about the way it is now too.