When it comes to musicians having flings with underage people, one has to wonder if they should ask their groupies for ID. I'm not even being flippant or sarcastic BTW
If a musician actively grooms a younger person then knowing that happened would seriously taint their music, but failing to check their age when they meet backstage? It's obviously not the fault of the person who's not able to consent, but on the part of the musician it's more a lapse of responsibility than predatory behaviour .
Tangent aside
It'd depend on what they'd done, and how much I liked them before