Really....

I would think of people being prudes who think bad of it. There should be much more older women dating young men, it would make society more healthy. Think about it:
-The young men can have sex
-Old single women can have sex
-It will be easier for the men to find real dates later, because old women know a lot of people and can also teach them dating-stuff.

It's a win-win for everyone. What I think many do wrong is that they think such a relationship is about sex only. It should involve a friendship always, otherwise you could just buy a prostitute instead. You must share a hobby or interest like fitness/sports, massaging each other, festivals, gaming, creative design maybe, health-routines, music. It is of course a bit harder to find something you can do together than it is normally. If you don't value the other person as a real friend, like you would with other friends, then the sexual affair is most of the time also not really worth it so much. And you should be aware that the young man might want to marry someone else later and get kids, so it will nearly always be a longtime affair, that maybe can be paused and unpaused, but marriage is very unlikely.