In most media, there are problems; these problems generally being the misrepresentation of a minority, the mocking of a minority, or the under representation of a minority. "Buffy the Vampire Slayer", a show that ran from 1997 to 2003, is no exception. While I enjoyed most parts of the show, I acknowledge that it contains problematic elements. In BTVS, we see sexism/misogyny being used to advance plot, and complete lack of representation of non-white characters.
Rape is used to advance plot/create a new plot line in the show. Before I talk about the sexual assault in BTVS, let's start with a little bit of history on Joss Whedon's (a director and writer, and the creator of "Buffy the Vampire Slayer") reoccurring tendency to use rape scenes to advance plot lines in his work, and/or his tendency to allow rape scenes used to advance plot to be present in his work. In his latest Marvel film, "Avengers: Age of Ultron" (written by Whedon and released May 1st, 2015), Whedon managed to slip a rape joke into Robert Downey Jr.'s lines; yes, Iron Man made a rape joke about women in a Marvel movie. Let's rewind the timeline a bit: in "Dollhouse", a show that ran from 2009 to 2010, Whedon takes a character, Sierra, and writes the show so that she is the victim of repeated rape by a superior. Let's go back even further: "Buffy the Vampire Slayer", a show created by Joss Whedon. In the episode "Seeing Red" of BTVS, Spike attempts to rape Buffy Summers; Buffy crying and screaming all the while. Spike (her assailant) later jokes about the incident cruelly, smiling the whole time. This episode was not written by Whedon, but the fact that it existed in his show is very problematic.
The next most obvious issue in "Buffy the Vampire Slayer" is the exclusion of non-white characters in the show. The fact that you can count the amount of significant non-white characters that have ever been on BTVS on two hands is rather unfortunate: "...for seven seasons, 144 episodes, the majority of the Buffy cast is white and Black folks/people of color rarely appear and when they do they end up dead, with the exception of Robin Wood, the butt of some latently/overtly racist fun-having humor, sex objects, or doomed to disappear into set extra/side character hell" (https://eliasdiamonds.wordpress.com/2011/10/03/revisiting-whedons-buffy-the-vampire-slayer-2-black-folks/).