Apparently some people don't understand the term tsundere...
But in all honesty I can understand his "denseness" as self preservation. If everyone around me wanted me not for who I am but for their own fetish... or at least emphasized the fetish when dealing with me, I would probably assume they were simply using me as well...
And, no, it isn't solely about sex. If that's why someone is reading this then go find some hentai... (Some people actually want a relationship, any men who assume or assert otherwise are inhuman, needless to say the boys need to grow up...)