In between what the law bans and what the law permits, there's all the "you're allowed to do it because nobody said you can't" stuff. If you happen to be doing that stuff, it's comforting to have it explicitly called out as legal. If you want that stuff to be illegal, you obviously don't want it getting promoted to "more" legal, because it's harder to get your ban passed.
Imagine a new bill is introduced. "Eating apples is legal." The Apple Pickers Union would love to see this bill passed. The Orange Pickers Union would probably oppose it. They'd both spend millions on a blogocampaign to convince you they are right. But passing (or not passing) the bill changes nothing; it's already legal to eat apples.
> If you happen to be doing that stuff, it's comforting to have it explicitly called out as legal.
No it isn't; having the law explicitly call it out as legal shifts the perception of those activities from being ones that the law does not involve itself with at all to ones that are enabled and authorized by the law.
In other words, it makes things subject to the law that were not previously subject to the law, and so ultimately makes those things easier to constrain/regulate in the future.
"enabled and authorized by the law." I think if you're Facebook, that's exactly what you want. They would prefer to avoid lawsuits about sharing information, even if they would win those lawsuits anyway. I think Good Samaritan laws are an appropriate analogy. You don't want people worrying about liability instead of doing the right thing (right thing being highly subjective).
"easier to constrain/regulate in the future." Ironically, that sounds like motivation for the EFF to support the bill.
Imagine a new bill is introduced. "Eating apples is legal." The Apple Pickers Union would love to see this bill passed. The Orange Pickers Union would probably oppose it. They'd both spend millions on a blogocampaign to convince you they are right. But passing (or not passing) the bill changes nothing; it's already legal to eat apples.