Okay, that's probably not particularly relevant to this thread, but it popped into my head when I was reading this article.
Contraception and abortion are different sins; the latter is also a crime, since it is a sin against another. However, they mutually reinforce each other’s evil work: users of contraception come to regard abortion as backup contraception, and advocates of abortion “rights” consider contraception a benign alternative to abortion.
It is not unlike one sin begets another in general: thieves are also often murderers, drunkards are often gluttons, adulterers are also liars, etc.