You said 500k victims per year. those are numbers of sexual assaults, not rape, and yeah, grabbing butt without consent is considered sexual assault. I dont see what confuses you here.
Are you going on record stating inappropriate and unwanted touching is a minor thing? Again...yikes.
Non-consensual touching falls under the sexual assault label which itself is included under the sexual violence umbrella. That in no way equates half a million sexual violence cases to ~500k cases of butt grabbing. Not to mention, nonconsensual groping is a crime for good reason.