And there are plenty of responsible STDs responsible for infecting those responsible, promiscuous people with responsible diseases whose consequences they will be responsible for for the rest of their lives.
Something like 1/3 of all the single Americans between 20 and 40 have genital herpes. There's no cure. Think about that statistic, and see how "responsible" you feel about promiscuity.
Do you have substantiation for that statistic? I'm not saying you're wrong--it just seems high. The CDC Website places the total number of infections at 45 million, or about 20% of the adolescent and adult population. I'd be interested if you have a link to documentation for the higher statistic you cite for single young adults.