Before germ theory was fully understood and comprehended, the general theory behind disease was it was a punishment for sin and ungodliness. Therefore sexually transmitted diseases were the ultimate punishment for adultery - although crabs/public lice and scabies would have affected many people given the lack of knowledge about daily bathing/showering.
A world without STIs might not lead to such social taboos developing about sex and sexuality although the church would still battle against the orgasm imho. People like Beethoven, Oscar Wilde, James Joyce, Henri de Toulouse-Lautrec wouldn't have died earlier than they might have otherwise done.