I would tread exceedingly lightly. sɛҳuąƖ perversion is so acceptable in society that they may fall back into it without any real warning like a drug addict relapses. And it would be very unfair to any potential spouses to not be well informed of their perspective spouse's past. There's nothing like a nasty surprise to invalidate your marriage a child or two later. And hey, if they're really repentant and confident in their faith in Christ, then what's a few rumors? I'm sure there are plenty of rumors flying around about a lot of us who come to the Faith after a sinful life. It's not really the sin of the person with the past, but the sin of the gossips.
You say that it would be unfair for a potential spouse to not be warned of a person's sinful past. How could you warn them without committing the sin of detraction? Detraction would occur if the sinner had repented of the sin. So you are saying that if you knew someone who committed sodomy, and that person repented, that you would tell every girl at your Church about that person's sin of sodomy to "warn" them to never commit to a relationship with that person?
That to me sounds wrong. Marriage is a sacrament that is intended to prevent sɛҳuąƖ immorality. If you attempt to discourage someone from marrying a certain repentant sinner then you would be setting up the repentent sinner for sɛҳuąƖ immorality. Kinda like holding someone down and never letting them get back up. It might actually cause them to fall.
I said potential spouse. I didn't say every lady in church. If they don't know what their spouse's struggles are, how are they going to help them get to heaven?
It is a disservice not to inform someone about something that might invalidate their marriage, especially if you strongly suspect that they don't know. Hopefully, the person would inform their spouse about their past but that doesn't always happen.
That was the lovely surprise I got after two years of marriage. If someone had told me in advance what I may have to deal with instead of stuffing it down and hiding it, things would have gone much differently. If even one person had said that this particular sin was one he had struggled with in the past, I could have at least had the opportunity to mull it over and reconsider my abilities to deal with it. Heck, if one person had even asked me if I knew about it, that would've been a blessing! But everyone was trying to be all forgiving and not get involved with "dredging up his past" so when i discovered it, I was completely gobsmacked!
So, due to the desire of others not to detract my ex-husband, I now have a broken family, a strained relationship with my oldest child, a strained relationship with my husband and unnecessary hardship for my younger children who hardly see their sister because of years of custody battles. All of which could have been avoided by anyone willing to just make sure that I knew before we got married.