From what I've read about JWs and the indoctrination process, manners are something that could be a casualty. Manners are a way of showing respect to your fellow human beings. My understanding is that JWs are taught not to respect anything or anyone from outside the Kingdom Hall environment. Also, that they don't respect anything done in kingdom service; no-one gets a pat on the back for anything. That would be taking the glory away from Jehovah. The GB likes to use that bible verse that says something like "we are just slaves, we did our duty" (most other bibles translate "doulos" as "servant").
Against that backdrop of basic disrespect, I wouldn't see manners as being pushed as important. The arrogant higher ups could get away with disrespect for people lower down the pecking order, and their attitudes would be pushed down the line to those "lesser ones".
The OP seems to be of the opinion that you'll find manners and respect in the Kingdom Hall, but not among exJWs. For the reasons above, I don't see that as automatically being the case.