I don't think many would argue with most of your first sentence TM; however, us humans are designed to make mistakes. I've done a fair few deck landings and luckily have never landed on the wrong one, I've got a few personal processes that I use to minimise the risk because I've got the sort of brain that just screws up if I give it the slightest chance. I have never said 'It won't happen to me' in fact I know it would happen to me if I carried on long enough!
So, on the basis pilots tend to think 'Bugger, that's embarrassing, I've landed on the wrong helideck' the OIM might well think 'Jesus!! that idiot landed on my helideck while I've got scaffolders over the side and was just about to cold flare - we could have been blown to smithereens and lost men over the side'! Isn't it the responsibility of everyone to minimise the risk?
Cheers
TeeS