Let's go level by level for bardic mind control spells. There are other spells from other classes, but none have any especially different effects.
Level 1. Charm Person. which allows you to make temporary acquaintance with someone.
Level 2. Suggestion. This spell lets you suggest an appropriate action to someone. Calm emotions allows you to reduce people's anger that your bard is using magic to coerce people into sex.
Level 3 spells are pretty low on useful spells for manipulating people into sex, but there is one useful one called Fast Friends Which allows quickly befriending people.
Level 4 doesn't have any notably useful spells for compelling people to love you.
Level 5 does have several. Geas lets you impose a long term command on a person, modify memory helps your character establish that rather than being a rapist they are a friend.
Level 6 has a useful spell, Mass Suggestion which can force multiple people to take loving actions.
In terms of magical items, the Philter of Love forces people to love you.
That said, there is an easier way. Rather than using magic to coerce innocent people to love them or admire them and then raping them, they could simply hire prostitutes. This both reduces the need to roleplay what they are up to, and provides a less creepy way to have it on the table.