There is no double standard here.. to compare boobs with penis' is stupid. The main function of tits is to feed the offspring. The main function of a pecker is to impregnate the female. It's like comparing apples and oranges..no go.
Now, to take this to a ridiculous conclusion, the human female bosom is the most beautiful form in nature. However, I have NEVER heard any woman say "My, what an attractive scrotum you have." Same goes for dicks. Lets face it folks, they just dont measure up!! (to boobs)