Sex education teaches kids to understand and respect their bodies, then to manage relationships with other people in ways that are safe and respectful. It actually starts before kindergarten with the naming of body parts and understanding consent (no, not in a gross way!). Sex education is what helps the older kids make good choices and speak up for themselves, as well as keep themselves and their partners healthy and safe.
Anyone who wants to keep the 6th graders from learning about how to identify when someone is crossing their personal boundaries and speak up for themselves around personal boundaries is someone actively supporting the pedophiles and/or the confused kids who are going to pass around diseases.