I have talked to so many people who have given up on Buffy because they saw "one episode" and didn't like it. The thing about this show is that it's hard to "get" if you don't watch it. It's not your typical show.
I have shit tons of other fandoms. If you don't like Kevin Smith movies, I'll understand. I can see how it might not be everyone's cup of tea. If you don't like Harry Potter, I won't take you seriously unless you've read at least one book all the way through, but Rowling's writing isn't for everyone, I'll get it. If you don't like Pirates of the Caribbean, I'll understand. If you don't like American Idol, I'll understand, hell, I'll even sympathize (though I won't let you get out of the conversation until you understand that Simon really isn't evil).
But if you say you don't like Buffy, I won't buy it. I won't buy it unless you've given the show a solid, fighting chance, and one episode ain't no fighting chance. This is a show that spanned seven seasons, topping out at 143 episodes (yes, I'm counting season six's two hour pilot as one episode), several of which were, I'll be the first to admit, pretty crappy. But basing your opinion of a seven-year zeitgeist off of .007% of it is, frankly, stupid. What makes the show great is that it isn't definable by a single episode. Joss takes his characters through so many experiences, timelines and situations that weave in and out of each other over the seasons that understanding why fans are so obsessed with this show would honestly take watching the entire series.
But I'll let you off easy. Here's how to get the Whedon-mongers to leave you alone:
Offer to watch five episodes of their choice.
That's right, we're going to make you sit through five whole hour-long episodes. But when you consider the sheer mass of episodes out there? That's not too much to ask. And if your evangelist is a good fan, the episodes they pick are going to be good ones, defining ones, ones that will give you a gist of what the show is and why it's so loved.
And if after you watch those episodes, you're still not interested, you still hate the acting, it's still not your thing, well...I'll be bewildered, but I'll buy it. And I'll leave you alone. Because instead of bitching at us to leave you alone, you gave it a chance.
Audience Participation! I'm stealing the audience participation thing from wickedsin. It's a good idea! If you're a Buffy fan, what would your five episodes be? If you're not a Buffy fan, pick five episodes from your favorite show that you would use to "convert" an outsider. Also, explain to me why you're not a Buffy fan (I promise I won't get all snippy, I've snipped enough, don't you think?).
My five episodes:
1. Hush (S4, E10)
2. The Wish (S3, E9) (Bonus points if you watch this in conjunction with Doppelgangland, but it's not required)
3. Graduation Day, Pt. One (S3, E21)
4. Innocence (S2, E14)
5. Fool for Love (S5, E7)
ETA: Warning, slight Buffy spoilers for season 2 in comments