It's amazing the lengths people will go to to avoid a difficult conversation.
Whether you like it or not, you are a part of the total equation and if you have issues with it, you should try to communicate your concerns with all relevant people.
Once you have communicated your concerns, It's not your problem anymore.
People don't have to listen, don't have to do what you tell them to do, and they don't have to take your concerns into consideration.
If they choose to do something stupid that's on them.
If I see a 40 plus year old man and a 16 year old girl going places together, I'm going to assume the girl is his daughter.
Pretty high Ick factor.