You misunderstood. Alaska Airlines is not shutting down CC accounts; Alaska Arlines is shutting down FFP accounts which "smell" too much like nothing but churning and redeeming:
The above three threads are in the Alaska Airlines forum, and refer to Alaska Airlines shutting down Alaska MileagePlan accounts. They are not shutting down your BofA card (though any still-open BofA Alaska Airlines card becomes fairly useless if the Alaska Airlines FFP it's linked to is closed down ).

(This topic has also been discussed as a "side issue" in the Alaska Airlines card thread I linked in my previous post.)

Having said that: I've never heard of any other airline shutting down FFP accounts because of too much churning. Of course, AA would be just about the only other candidate, since Citi, its bank, is the only other bank I'm aware of that has ever allowed "very fast" churning of an airline credit card (about a decade ago, Citi allowed applying for 2 AA 25k bonus cards at a time, every 65 days, and getting the bonus each time with at most a three-digit spend requirement!).