Fornication is not like accidentally saying a swear word from time to time, a mistake, a "slip up". It can be a serious thing. My views might seem strict or harsh to some of you, but that is too bad. The bible isn't any less strict when it comes to fornication, so maybe you should familiarise yourselves with some of the apostle's teachings. 1. do not keep company with a christian who is a fornicator, and 2. the eternal consequences of fornication.
1Co 5:9 I wrote unto you in an epistle not to company with fornicators:
1Co 5:11 But now I have written unto you not to keep company, if any man that is called a brother be a fornicator, or covetous, or an idolater, or a railer, or a drunkard, or an extortioner; with such a one no not to eat.
Unrepented fornication has eternal consequences , and is on the same level as idolatry, adultery, and homosexuality:
1Co 6:9 Know ye not that the unrighteous shall not inherit the kingdom of God? Be not deceived: neither fornicators, nor idolaters, nor adulterers, nor effeminate, nor abusers of themselves with mankind,
Rev 9:21 Neither repented they of their murders, nor of their sorceries, nor of their fornication, nor of their thefts.