Roger,
Your last sentance is hard to understand, and your attitude is just the type that I wish didn't exist in birding.
The only one of your reasons that is valid is the lack of parking space for visitors; then again Broad-billed Sandpiper isn't that 'big' a bird so the chances are that there wouldn't be many cars parking there anyway. Besides, not many people are going to be irrational enough to block people's driveways (although it does occasionally happen and those who do such a thing should accept full responsibility).
Seriously what kind of joke is it to try and claim to other intelligent adults on this forum that the cafe would not be able to cope and wouldn't want the hassle?! Have you even asked the owners about such a situation? As Paul says, a cafe like this would surely welcome a small to medium-sized influx of birders and a temporary upturn in trade; it's not as if a Broad-billed Sand is going to attract four-figure totals of people - this is no Willet/Hudwit/Tattler we are talking about here.
Your storm situation is unrealistic. If foul weather is forecast, people can easily make the decision as to head to Alkborough or not. I suspect that those who are less fortunate than ourselves when it comes to swimming would not run the risk before setting out. Was there a storm that caused flooding whilst the Broad-billed Sand was present? I don't think there was...
So I'd like to finish by contrasting with Roger has said - if you find a rare bird at Alkborough Flats, or any other place, don't be lured in to suppression by people with attitudes such as the one above - I thought this was a thing of the past, but obviously not. Keep on reporting birds, and share them with others - then there is no chance of being brandished selfish
Cheers
Josh