When and why did necromancy became a bad thing?
Probably since it was first practiced. However, there are no sources that ancient that have survived to our day. Some people would have been against it from day one because they would have thought it unholy and unnatural to the lest.
The oldest literary account of necromancy is found in Homer's (12th-8th ...
Actually, trafficking with chthonic spirits could be prosecuted as impiety under Greek law by classical times.
The Witchcraft and Magic in Europe's second volume, on ancient Greece and Rome, has some interesting stuff on this.
This question has now been answered:
quote identification — Literature Stack Exchange
… those who attribute the quotation to Walsh are misattributing and/or misquoting.
The direct quotation originates with Ralph Woodrow, who paraphrases and cites, but does not quote, Walsh.
… page 152 in chapter 20 of Woodrow's Babylon Mystery Religion.
In myths, humans follow a limited number of patterns, regardless of their cultural background. This field of study is called Comparative Mythology. This has uncovered a number of parallels, or archetypes, between the myths of different cultures, including some very widespread recurring themes and plot elements, like:
Creation of mankind from clay
Bans on necromancy are hardly a new thing. The Bible explicitly forbade it 3500 years ago:
There shall not be found among you any one that maketh his son or his daughter to pass through the fire, or that useth divination, or an observer of times, or an enchanter, or a witch, Or a charmer, or a consulter with familiar spirits, or a wizard, or a necromancer. ...