Over the years, cartoonists and writers alike have been asked (and accused) of publications like comic books and pulp magazines are sexist towards women. In past publications, comics did have sexist qualities, but sexism never became an inherent part of the comic book culture, frequent as it was (and is). Ever since "jungle heroes" like "Sheena, Queen of the Jungle" came into existence, details like costuming, dialogue, and general appearance came into question.
Most of the sexist accusations fall on superhero comics, though that is definitely not the case. The teen and adult romance comics increasingly condescended to women and their opinions. Of course they did not receive most of the finger-pointing, although they were closer to real life than superhero comics ever would be. Considering the 90% male audience, superhero comics had the most impact on their views of women, which most writers took to their advantage.
Even though most female characters were represented as sex symbols rather than superheroes, one stood out with a blatant message. Creator William Moulton Marston modeled "Wonder Woman" and her heritage after the Greek Amazonians. Princess Diana of the Amazons came from a man-less planet that was blessed by the gods, a reflection of what Marston thought of the future of civilization. Her powers excelled the gods' (and in some ways, were comparable to Superman's), and her tools were as efficient as Batman's. Depending on the writer and artist, sometimes Wonder Woman's features would be too risqué, or her clothes too short. At other times her entire personality (and capabilities) would change (such as one point where Diana actually lost her powers and used martial arts instead, taking her down several notches). Nevertheless, she is one of the longest lasting superheroes in existence, and a continuous symbol for female strength.
Costuming is probably the worst offense when arguing sexism in comic books. It creates the notion that the ideal woman has an extremely disproportionate body type. However, comics are not just sexist towards women. Even if the men are seen as juggernauts, that description of the general "accepted" man is just as inaccurate as the women with exaggerated legs and breasts. It could be argued that men have every right to feel just as insecure as women do, if not for one big factor. Most super-heroines received what are called "defensive powers", and that can be seen as another form of inferiority. The heroine would be the protector or nurturer rather than actually "save the day" with her own abilities. With characters like Jean Grey, the powers she received became too much for her to handle, and the writers make her destroy a galaxy due to her loss of control, ending with her death. Another example of sexism can be found in origin stories; Wolverine is an animalistic, trained killer from Canada; Superman is an "alien messiah"; The Dazzler is a washed up disco singer who loves roller-blading and turns music into light sparkles with her hands. In some cases, though, sexism is pretty even, if you compare the origins of Falcon (an ex-pimp with the nickname "snap") to Storm (an African "goddess").
Sexism was not only apparent in the clothing choices for superheroes and heroines, but the dialogue as well. In a few issues of the Green Lantern, Hal's choices of words are enough to send the female rights movements back about eighty years (I mean, seriously, look at this). Dialogue like this appeared in most issues, subtle or not. It really depends on whoever is writing and drawing these characters. Publishing did not seem to make much of a difference either. Both DC and Marvel exploited sexist ideals for whatever reasons.
Comics are sexist, and there are not many ways of getting around it. It is, however, a matter of how they are sexist. Some of the artwork is ridiculous, the body proportions are terrible, and in some cases, the costumes could be painted on. Overall, older comics in the 1930s-1970s were more inclined to be sexist, but not purposefully. There was not as much censorship as there is today; the 1948 Comic Code and the ones afterwards drew a line as to how much sexual content is presented (if any). Many people can consider comic books in the present to be sexist as well, with costuming as their leading argument (see Power Girl). Recently, more women are getting involved with the comic book industry (such as writer Jodi Picoult, no matter how trite her story on Wonder Woman is). Comic books will most likely be under persecution for things like this forever, but they do continue to entertain.