Basically, masturbation wasn't thought of as being that big of a deal throughout history and nannies in the 17th century even used it to put boys to sleep [1] but that would soon change when two anti-masturbation pamphlets were published (the 1st one was anonymously published in 1716 and the second was published in 1760 by Samuel Auguste Tissot) which alleged various diseases and afflictions i.e. impotence, gonorrhoea, epilepsy, gout, rheumatism etc were caused by masturbation. links [2] and [3] go into more detail and the first place I heard about this [4] was a Cracked.com article (but for those of you who know their SJW slant, 1. this is from 2011, before they want overboard with Social Justice, and 2. if you don't trust them, then at least take a look at their sources to see if their lying)

[1]-(https://en.wikipedia.org/wiki/Masturbation#History_and_society) [2]-(http://www.circinfo.org/Circumcision_and_masturbation.html) [3]-(http://www.cirp.org/library/history/darby4/) [4]-(http://www.cracked.com/article_19520_5-insane-ways-fear-masturbation-shaped-modern-world.html