For what I know AC is not a big fan of the country music stuff whereas Mark was in it.
AC only NHB gig was because Guy wasn't available for it. You can also consider the fact that Alan is also a Geordie.
I also don't think Alan is the only example of "pissing on his chips" . In fact this is not a new phenomena for Dire Straits. Let's look at a few similar examples -
David Knopfler - we know that story
Tommy Mandel - tried to improvise
Hal Lindes - booted during early BIA sessions
Pick Withers - got fed up
Jack Sonni - "had two lovely girls" then never got invited back
Terry Williams - didn't play how MK wanted on BIA but did a sterling job on tour, wanted to play on OES tour but never got invited back
Alan Clark - obviously loves playing the DS tunes but not as obedient as lap dog Guy Fletcher
Could it not be that rather than "pissing on chips" these guys simply challenged MK in a way he didn't like, or could control??