Birth control pills are hormones which mimic the natural hormones which the body secretes in order to achieve certain outcomes.
When menopausal women take synthetic estrogens in order to stave off heart disease and alleviate the unpleasant aspects of menopause (hot flashes, "brain fog," insomnia, emotional lability) -- are they taking poison? How about post-hysterectomy women?
When elderly men take synthetic testosterone in order to continue to have full sexual function, not to mention improved wound healing and normal muscle mass -- are they taking poison?
What about men with prostate cancer, who take estrogens in order to stop the growth of the cancer? Is that poison?
When menopausal women take synthetic estrogens in order to stave off heart disease...
Granting your premise, then in this case, can the medication be properly called "birth control," since the primary objective is "staving off heart disease"?
My assertion regarded "the pill" when it is used as a method of birth control, which is by far its most common use.
In fact, "the pill's" usefulness for treating disease is extremely limited, according to the opinion of doctors that I trust.