Argumentum ad nauseum. You can take anything to the extremes and show it is silly. Like drinking water...too much is a medical emergency, so you'd argue don't drink any at all?
If I spend $2k to get to a liveaboard and $3k for the dive boat -- times 2 for me and my wife -- and then the trip gets turned around because some egotistical self-centered idiot refused to disclose a recent heart valve replacement, do I have a right to be upset? You betcha. He was willing to take the risk....but he also had a huge negative effect on 20 other passengers.....did he have that right? He should not have been on the boat. Now, if someone on the same trip -- minus the idiot -- is in great health and never the less has a heart attack, then that's life. He did nothing purposeful to negatively affect me, unlike the idiot.
This is rather unlike your examples. Flying on an airplane is not typically a life-threatening activity, unlike diving. Riding on subways, night clubs, hockey matches.....I'm not out $10k and my week of vacation if something goes awry.