Where It All Goes Down
Célimène's house; Paris in the Seventeenth Century
Cool. This should be easy, because the entire play takes place in one society's chick's house. Right? Well, sure, until you remember that there's a whole (rapidly expanding) world outside Célimène's door.
Europe
Let's take a trip back in time to the seventeenth-century Europe. We're juuuuust about to enter the modern era but haven't quite made it yet. The French Revolution and the Enlightenment won't happen until the next century; no one's harnessed steam or gotten too excited about coal. London is still having plagues, the English Civil War is happening, and people have just discovered central banks, tea, and coffee.
This is a long time ago, guys.
In France, Louis "The Sun King" XIV was in charge and playing Pokémon with new French land. You know, "Gotta catch 'em all." New France, already took up a large swath of American land. You know who Louisiana was named after? Yeah, this guy, whose ego was so huge that Louisiana stretched from present day Louisiana all the way North to Canada.
Paris
But no one actually wanted to live in New France. (Except, presumably, the people who were already living there.) Everyone in Western Europe agreed: Paris was the place to be. It was the center of art, culture, fashion, and general awesomeness. Tons of people were moving to Paris every year and the city was getting bigger and bigger to fit them all in.
Sure, Louis would eventually run away to Versailles, but when Molière first performed The Misanthrope in 1666, Paris was where all the hip happening people were doing their thing.
Nobility
Nobility was a pretty big deal. If you were born into a family with a title, you had it made. It wasn't just that you were richer than commoners; you were actually different. Like, almost a different species. And there were all sorts of laws to make sure that the established order stayed established.
For example, poor people couldn't wear the kinds of clothes the nobility could, not because they couldn't afford it (although they couldn't), but because it was illegal. According to these sumptuary laws, only nobles could wear fancy gear made out of fabrics like silk, fur and velvet.
See, the problem is that nobles would give their old clothes to their servants—that was a perk of the job, like getting a discount on your cell phone plan or a free gym membership might be today. But they didn't actually want servants to wear those clothes, because, you know, that might lead to anarchy. Enter sumptuary laws. Because servants were legally forbidden to wear the old clothes, they sold them to rag merchants.
Also the nobility was expected to act a certain way to show that, well, they were noble. That included throwing huge parties, building lavish houses, acting all proper and refined, and defending their honor. But, by the time Molière was writing The Misanthrope people were getting pretty tired of all of the hullaballoo about noble people, since all their fancy clothes, lavish parties, and big mansions were built on the sweat, labor, and taxes of commoners.
Plus, the nobles weren't exactly acting noble. Instead of being honorable, setting a good example, and helping out the poor, they were acting like a bunch of spoiled rich kids. Some people—shock and horror—even said that the whole system of nobility was stupid and immoral. Writing at about the same time, Blaise Pascal was in such a huff about it that he devoted a whole section of his Pensées to how nobles should stop patting themselves on the back so strenuously: "Your soul and your body are, of themselves, indifferent to the state of boatman of that of duke; and there is no natural bond that attaches them to one condition rather than to another" (source).
Salons
Even more than oppressing the commoners, nobility loved to go to salons. Salons were the popular thing to do if you were a member of the nobility. You would invite your friends over to your living room (or sometimes your bedroom) and chill while talking about poetry or philosophy or other smarty-pants things like that.
This was before you could just Facebook your friends or Wiki anything you wanted, so it was an easy way to figure out what was going on in the world. Some people say that the focus of the salons was academic stuff, but others say it was more about polite conversation.
Either way, the idea is that they were supposed to be refined and elegant as a reaction to earlier aristocratic society, which was all about aggressive forms of masculinity: hunting, whoring, drinking, and generally carousing. Basically, a bunch of noble ladies got together and convinced the aristocratic guys that they would really prefer someone who would sit and talk to them instead of spending all their time hunting and drinking with a bunch of other dudes, KTHX.
Célimène's House
OK, so what's the point of all that history? Well, Célimène's house is a tiny version of French society at large. If you're feeling frisky, you could even call it a microcosm. It's really important to think about the atmosphere of France, and Paris in particular at the time.
Most of the play takes place in Célimène's salon. We can tell that Molière is making fun of the whole salon system, because Célimène and her friends definitely don't talk philosophy, and they don't even just practice their small talk. Nope, they get down and dirty with their gossip. Even Éliante knows that it is inevitable, and she tells Philinte, "And all our dear friends' ears will shortly burn./ The conversation takes its usual turn" (2.5.33). In other words, this isn't a one-time thing—the whole point of Célimène's salons is to talk smack.
So, it's easy to see why Alceste is just too fed up with society. Just like other people at the time, Alceste thinks that all this hoity-toity stuff has gone on for long enough and now it's just ridiculous. Think of him like someone going off about how he's so sick of our consumerist, reality-TV-show culture, and you'll get the idea. He's got his finger on the pulse of the times, and he thinks there's something wrong with the heartbeat.
The last big thing about Célimène's house is that we can read it as a symbol of her openness. Like, Alceste is not the kind of guy who would organize a salon. He doesn't like people. He probably locks his door and pulls down the blinds when he gets home.
Célimène is the total opposite. She lets anyone and everyone into her house, just the same way that she welcomes society (and a whole bunch of dudes) with open arms.