I think it's okay for a 16 year old to date a 24 year old
Why do you think it's okay for a 16-year-old to date an older man?
Their old enough to date so that's it.
You shouldn't condone adults dating children, because even teenagers are still too young to make important decisions.  People's brains continue to develop into early adulthood, and besides, it's illegal to have relations with anyone under 18.
Legal is not moral, I know this much.
It's wrong to suggest that a 24-year old and a 16-year old having a relationship is appropriate. Mentally, physically, and emotionally this relationship would be inappropriate.