Into every life, a little "David" (or someone like him) must fall. You might know the type already: a kind-of-jerky guy who passes off his ridiculous behavior (and, often, avoidance of steady work) as being a creative type.
Right now, David teaches communications classes in an adult education program, but it seems like he's kind of a dilettante (a noncommittal dabbler); he used to sell Bibles and attended seminary at some point in the past, and he's also making a film whose plot he hasn't yet determined. (Basically, though, it consists of random things he feels like filming or thinks are cool—and it's called Random Samples. So, yeah, he can probably skip writing an Oscar speech.)
We get hints that there's no real meat to David's artistic vision when the narrator tries to press him for details about it: "'How can you tell what to put in if you don't already know what it's about?' I asked David when he was describing it. He gave me one of his initiate-to-novice stares. 'If you close your mind in advance like that you wreck it. What you need is flow'" (1.14). Sure, we suppose that could be true, but David's real talent seems to lie in being haughty and condescending to other people and only claiming to be an artist and thinker—without really ever coming up with the artistic or philosophical goods.
As you might have gathered from his apparent fondness for "initiate-to-novice stares," David really isn't that nice of a guy—in fact, we quickly discover that, in addition to being vapid and condescending, he's quite the sexist bully.
Exhibit A: He makes an executive decision that they should all stay at the cabin for several extra days, without ever asking the narrator (you know, the one whose family owns the house) if that's okay. Anna outright says that she doesn't want to stay, but he totally disregards her opinion. Hmm, is it a coincidence that the two women in the group basically get zero respect from him? We think not.
Then there's the fact that he spends a lot of the novel trying to draw the narrator into dirty innuendo and behavior in front of his wife, humiliating Anna in various other ways, and railing against Americans for being "Pigs" without ever really providing any specific information about why he hates them, of course.
His sexual harassment of the narrator—often, but not always, undertaken for the express purpose of hurting his wife—gets more egregious as the novel goes on. You get a good example of all of "jerk" tendencies already described, plus his tendency for being condescending to women, while he's metaphorically patting the narrator on the head for not agreeing to sell her family's cabin to an American who had expressed interest: "'Good girl […] your heart's in the right place. And the rest of her too, he said to Joe, 'I like it round and firm and fully packed. Anna, you're eating too much'" (11.58). Pretty… er, "impressive" how he manages to cram that much jerkiness into one sentence, no?
He even criticizes Anna's weight when he's trying to get her to strip down naked for some random footage for his Random Samples. Understandably, she doesn't find the prospect super-appealing, particularly given the "fat" shaming, but he harasses and threatens her until he gets his way.
These are just some examples of his ridiculous and awful behavior, so we'll stop—but yeah, he's the kind of guy you avoid (and definitely don't invite out to an isolated cabin).
Although David's bullying and harassment of others are really not laughing matters, there is a bit of black humor to Atwood's portrayal of him. The narrator ultimately seems to view him as pretty ridiculous and cartoonish, constantly comparing him to cartoon characters such as Goofy (18.22) and Woody Woodpecker (16.42). It's hard to see someone as threatening when they're laughing like a cartoon character, but David somehow manages, and the effect is that he seems really grotesque.