Uhm, I wash by hand, my neighbours wash by hand, and I know a lot of people who do so. Even so, I never heard someone claiming she was washing the costume by hand... what I heard -and the image the statue gave me, individually- was that MJ was sorting the clothes before putting them in the washer, which is actually part of the whole process of washing the costume, even if we don't see her putting it into the machine.
In any case. Intent does matter, but so does the perception the public has upon the image. Taking your Batman example: Sure, in the comics he isn't a pedophile, and he has never even thought about Dick that way, but has that ever stopped subtext-reading?
The main problem with the cover was that it was too much like a tentacle-rape hentai cover. Even when that wasn't the intent (Because I'm going to give everyone involved the benefit of the doubt), that was the end result. Given that the artist is japanese herself, I highly doubt that she wasn't aware of the sexual connotations of a tentacle in her own culture!