Most of the trainers dont really dress like a realisicly in the Pokemon series.
I dont think GameFreak was trying to be sexist or make you look whorish, I think they were going for a character design that fits into the Unova region.
And it does. Unova is a high population, advanced place compared to Kanto, Hoenn, Sinnoh, or Johto. Obviously the characters will have a more modern dress style. And the shorts arent skimpy, it looks like a relatively acceptable futuristic dress style (compare that to Diamond/Pearl's skirt... Im sure that helped in the Frozen region of the game...) Even then, the skirt wasnt really that slutty or show-offy: they dont have your character do overly sexualized bends or include any fan-service.
Now, if they started showing panty shots, or gave a character a thong, then it would be time to be offended.
But look at Jessie from Team Rocket. Thats 100x skimpier than B/W.
Also, the Male characters dress isnt that much better. Considering the fact that the only male to look different in the series came in Ruby/Sapphire/Emerald, the male is just the same skin with poofier clothing.