The poem
Down, wanton, down! Have you no shame That at the whisper of Love's name, Or Beauty's, presto! up you raise Your angry head and stand at gaze?
Poor bombard-captain, sworn to reach The ravelin and effect a breach-- Indifferent what you storm or why, So be that in the breach you die!
Love may be blind, but Love at least Knows what is man and what mere beast; Or Beauty wayward, but requires More delicacy from her squires.
Tell me, my witless, whose one boast Could be your staunchness at the post, When were you made a man of parts To think fine and profess the arts?
Will many-gifted Beauty come Bowing to your bald rule of thumb, Or Love swear loyalty to your crown? Be gone, have done! Down, wanton, down!
This is a poem about a man who has an erection at an inopportune moment and is disgusted with his Johnson for being so indiscriminate and lustful. He's shouting at it to go away. It's an example of the struggle between head and little head.