Faust puts it very well, though I would add: don't kid yourself. A scantily-clad woman is still a scantily-clad woman, whatever plot-related reasons may be involved. Be careful and clever about it.
In case you never figured, it was a test statement. If someone feels the need to portray scantily-clad women, does it play any
purpose? It wouldn't even be worth it just for the sake of having it (unless the media is being targetted towards teen boys, which is... kinda horrid). It's the question I always ask myself while writing: what's the purpose of the element in the story? Why a vase and not a clock? Why burgers and not hotdogs? Why Libra but not Virgo? Why a dagger and not a rod? These questions help you analyze the plot abstractly and help rid of any "author's bias" temporarily which helps see things from another perspective. These are also essential for good mystery / thriller writing. XD
In this case, scantily-clad women, sexism or not, wouldn't even be an effective element in the story unless there's some explanation to it (and a
pretty good explanation at that). Unless the situation is about beach parties, communal baths, etc. where even scantily-clad men are found everywhere, there's simply no reason to have it.
Then again, the topic may split here to "what do you mean by scantily-clad". Is it clothes altogether or just the armor?
If it's the latter, that complicates things further because 99% of the population are usually civilians and don't have armors. So if a woman is injured in warfare and doesn't have armor that does not mean the author was biased against her -- she's just a civilian, like many other men who died right there.
An easy fix is equal-opportunity fanservice-- take care to make the males attractive to various people who are attracted to men.
Unfortunately, I can't do that. I'm not attracted to men. XD
That reminds me. When I went broke once I offered to write a story for a magazine. The short story was actually an excerpt scene from a novel I had "planned" but had no intention of writing. While sexism wasn't central to the story it did play an important plot-point, and I took the opportunity to do something I wouldn't have normally done: I included scantily-clad women. Only this time, the element had a purpose in the plot.
At first I was worried, but with the response I received upon the publication of my article renewed my faith in humanity.