I do not believe that contraceptives negate the negative effects of promiscuity if applied right because they have nothing to do with promiscuity. I believe that promiscuity is a spiritual problem.
Below is the standard I live by and what I believe is moral behavior. This no doubt this standard seems unreasonable to most people only because we are at a spiritual low water mark in history. Keep in mind it was written over 50 years ago and how much more decadent society is is today:
“The proper use of the sex instinct is the natural right of every individual, and it is precisely for this very purpose that the institution of marriage has been established. The Bahá'ís do not believe in the suppression of the sex impulse but in its regulation and control.”
Lights of Guidance (second part): A Bahá'í Reference File, pp. 364-365
“The Bahá'í Faith recognizes the value of the sex impulse, but condemns its illegitimate and improper expressions such as free love, companionate marriage and others, all of which it considers positively harmful to man and to the society in which he lives. The proper use of the sex instinct is the natural right of every individual, and it is precisely for this very purpose that the institution of marriage has been established. The Bahá'ís do not believe in the suppression of the sex impulse but in its regulation and control.'
In response to another letter enquiring if there were any legitimate way in which a person could express the sex instinct if, for some reason, he were unable to marry or if outer circumstances such as economic factors were to cause him to delay marriage, the Guardian's secretary wrote on his behalf:
'Concerning your question whether there are any legitimate forms of expression of the sex instinct outside of marriage: According to the Bahá'í Teachings no sexual act can be considered lawful unless performed between lawfully married persons. Outside of marital life there can be no lawful or healthy use of the sex impulse…….
In another letter on the Guardian's behalf, also to an individual believer, the secretary writes:
'Amongst the many other evils afflicting society in this spiritual low water mark in history is the question of immorality, and over-emphasis of sex...'
This indicates how the whole matter of sex and the problems related to it have assumed far too great an importance in the thinking of present-day society.
Lights of Guidance (second part): A Bahá'í Reference File, pp. 364-365