If I were to be kind, I’d say “How to Lose Friends and Alienate People,” based on Toby Young’s razor-sharp 2003 memoir on his failed writing stint at Vanity Fair, is a passable, uninspired romantic comedy masquerading as a satire. But I don’t want to be kind, mostly because screenwriter Peter Straughan wastes boatloads of promise on mindless slapstick. No, “How to Lose Friends” is, in fact, a toothless satire that devolves into an insipid, grating rom-com with a paint-by-numbers ending. Simon Pegg (so great in “Hot Fuzz” and “Shaun of the Dead”) figures prominently in said ending, starring as Sidney Young, a British tabloid journalist who takes a job at NYC’s Sharps Magazine, owned by tycoon Clayton Harding (a ho-hum Jeff Bridges). A rebellious, “principled” writer, he ignores the magazine’s caste system and clashes with everyone, including snarky but kind coworker Alison (Kirsten Dunst), a slimy editor (Danny Huston) and a sexpot young actress (Megan Fox). Director Robert B. Weide ruins good performances — Pegg is droll and delightful; Dunst is sweet, not cloying; Fox is, well, a fox who understands comic timing — with far-too-long gags involving pig urine, a dead Chihuahua, half-masticated sandwiches and more. Ugh. Go see “Beverly Hills Chihuahua” instead; expect twice the bite and half the crushing disappointment.