A bit of a long shot perhaps . . .
Moonface and Saucepanman were residents of The Faraway Tree. So a person who wouldn't be very popular with them would be someone who cuts down trees. However most of the obvious answers (such as lumberjack, logger, forester, etc) don't have 7 letters.
One other possibility though is that a SURGEON (which at least, has the right number of letters!) might be unpopular to tree dwellers as, to them, it would mean a tree surgeon.
Oh well, I tried anyway ;-)