Why would it only matter concerning opposite genders, in this day and age, isn't it also possible to jump to conclusions about same sex companions? Now, if these people were doing something like kissing, hand holding, or something else suggestive of a lot of familiarity or intimacy, maybe. Otherwise, I have come to think that it is quite difficult to anticipate or control what others think. Jesus was seen in the company of tax collectors and even questionable female companions possibly.
In my opinion, and that is all it is, I don't find reason for a lot of concern if they are not checking into a hotel, parking behind an abandoned building, etc, things done in public, could quite possibly be quite innocent, and I would grant them the benefit of a doubt.
I was ratted out to my pastor once, because I was drinking apple cider, someone assumed it was champagne. I know first hand that you can be seen as a sinner when doing something that is perfectly okay, so I have learned to be very cautious about making assumptions.
At the same time, I think it would be wise of your freind's husband, to consider how things look, as we all should.