This is a Dangerous topic.
"Guy" is a colloquial term which is not meant to imply masculinity. Substitute "Person".
A "Bad Guy" is the term used for either a theoretical or real agent of opposition to one's favored something. Often this term is applied in cases where labeling an assumed party would be Dangerous. This concept is also widely and sometimes jokingly used to label ethereal parties in "conspiracy theories".
- For a guard discussing security preparations for a bank, a robber is the "Bad Guy".
- For those seeking greater knowledge a person who distributes false information is a Bad Guy.
- For a systems administrator discussing the hardening of a network, a cracker is the "Bad Guy".
These are people who are opponents of or Desecrate Good Things.