“Somebody on Twitter once wrote of me, and it was a friend who sent this, ’Whoever the hell this guy is, he’s really cornered the market on inept bad guys,” says Scott MacArthur . “That made me laugh.”  It’s been an hour into an April coffee with the actor and writer, and the conversation is only just turning to his career. The anonymous assessment of his earlier work holds some water. MacArthur’s been the kidnapping welder in El Camino: A Breaking Bad Movie , the blackmailing stuntman in The Righteous Gemstones and, perhaps most memorably, the lovable dirtbag boyfriend to Kaitlin Olson’s character in cult Fox comedy The Mick . But before getting to all of that, or the hat trick of jobs that have made the Running Point actor hard to avoid in recent months, MacArthur first had to talk through some dog problems. Moose, his 18-month-old Ridgeback, has been picking fights with much larger peers in the local dogpark.…