The thing here is that nuclear is actually a poor metaphor. Because it would imply that the menace of Google, Amazon etc. doing something similar to what Tumblr did would be enough. It's not. Politicians don't understand the web, that's why they want SOPA. They surely did not understand nuclear weapons before a few of them had tragically been used.

That said, I also think that it would be preferable that big internet companies do not get to do what is described in the story. But not for the same reason as you seem to think. Here is my sweet dream: What I would like is for people to go on strike and to get down in the streets until SOPA is dead. Because that way politicians and all those who/which are backing SOPA knows what the web is capable of, without the web needing big private companies to back people up. Because some companies may be on the web's side for now, but everybody should keep in mind that these are companies, which mainly want/need to make profit. For this fight and for now the interests are the same so it's okay to use them as objective allies. It's never okay to really depend on them.

What this really is, is legalization of asymmetric warfare, and while a minority of tech/content companies might prefer things the way they are, they'll prosper just fine after SOPA is passed. This will only ever existentially affect the small.