Why destroy Laketown's bridge?

[Sauron the White]

Of course, had Smaug been able to land in the middle of Lake Town, destroying the bridge would've made no sense, as you pointed out. We'll have to assume he couldn't.

That assumption is convenient and contrary to how I read the story. Laketown brings in lots of goods by boat. They have dock areas which would be suitable for any such landing. You discount the idea of landing on roofs - something which I do not, even if it is just to help him slow down and hop off.

If Laketown is that crowded with small structures that there is no place to land, how would Smaug get around the town while on the ground anyways?

What purpose would there be for him to actually walk across that bridge?

Again, why destroy the bridge? To stop Smaug? How does that stop him? What it does do is cut off the quickest route of escape of the town residents and that does not seem very bright.

Why does a creature who can fly and attack from the air need with a land bridge? It simply makes no sense that I can see.

I agree that if a land based army was marching on your town, then you may want to cut yourself off from them in that fashion. But the attack was clearly by air and the people of Laketown knew that he was coming by air.