It may be the pride of continued association, or perhaps a weekend all-expense trip paid to a neighboring city. It is a sin against God, against His will, His word and His way. Judgement will fall on those who are guilty of fornication and who fail to turn in repentance. For I am guilty. The guilty Corinthians were forgiven, redeemded.
Fornication is a sin against the other person involved.
It is always a mutual sin engaged in by two or more. Involving others in your own sin, You sin against them. If your convictions had been strong perhaps they would have been encouraged to do right. The sin, the shame, the wrong is shared by both. Temptation is not a sin fornication is.