Contrary to what HWA portrayed in this letter it appears that HWA removed Garner Ted Armstrong was that he decided to side with Stanley Rader during a vicious power struggle for control of WCG. Essentially HWA had decided to removed his own son in favor of Stanley Rader in order to eventually make him the number two man in WCG. There is suspicion that Rader had damaging information on HWA and was able to blackmail him. Even though Rader later fell out of favor HWA continued to shun his own son and miserably failed to mend relations with him or his followers till the day he died.
All this and more are discussed in posts I made discussing The Truth Shall Make You Free by John Tuit (1981).
Please note, this article of HWA's disfellowshipping of Gerner Ted Armstrong is placed in a COG splinter group whose leader, M. John Allen, has now rejected much of what HWA taught and has embraced all sorts of heretical nonsense HWA never taught, as may be seen in a previous post:
Apparently M. John Allen now believes God is the Universe, and that Yahweh is not God but a leader of a bunch of space aliens who live on a planet called Nabiru. ...
I know I am wasting my sympathies but I feel sorry that he has fell into such craven nonsense. It is terrible that he is tries to lure people into believing these absurd and ridiculous ideas.