we can't also forget the use of photoshops on male models as well. although not as prominent, there are male body image issues as well as females, so its humans all round that are being targeted for their superficial appearances.
i don't think photoshop is the root cause of insecurity, it is rather a symptom of a disease known as media and societal expectations. photoshop is pretty much something that aggravates our own insecurities than stem from the impositions media and society has placed on us, in terms of aesthetic appearance and whatnot.
of course, photoshopping images to distort the body shape is wrong, but its not enough to simply eradicate it. we need to address the root causes of why we're so obsessed with photoshopping out imperfections and target the (unfortunately) overbearing and destructive ideals that are upheld within society today, in relation to body image and outward appearances.
so i disagree with you that photoshop is the why females feel inferior in the "looks" department, but it is rather the expectations of society that have been imposed upon both females and males that makes everyone feel like a piece of shit when they see billboards or media with perfectly sculpted humans on it. photoshop is simply a channel of our obsession with aesthetics and outward appearance, not the root cause of our insecurities.