In one case as we were sailing very close to a reef, one of the sailors said "well if we hit it, you do have insurance right?" and he was not joking.
In my opinion that attitude is just wrong, very wrong.
Also I would really question his experience as anyone I know with real experience would err on the side of safety.
Let's say for the sake of argument that this guy knew this water completely and had been sailing the same spot for 50 years and was 100% sure he was safe why would he terrify a new owner. That is just mean.
If it's a friend have a heart to heart and make him apologize and never do it again. Sometimes our friends take liberties because they have known us so long.
If it is just an acquaintance you know what to do.
It will never happen again because you will have the "talk" above and you will simply assert your right to have the boat follow the more conservative course.