“It seems to me that the popularity of activism and protesting do little to affect change…”
What makes you think that? Most major shifts begin with activism and protests. These are the ways that the populace makes their voice heard in large masses, much like lobbying is typically the way corporations have theirs heard. Sometimes protests go unheeded, and sometimes this leads to revolutions. Other times, the protesters disband without having achieved anything. The protester was named person of the year for 2011 because of the clear effects that protesters did have in 2011—from the Middle East to Europe. The true effects have even been felt here, in the form of the Tea Party, though that was before 2011. Occupy has had less success in achieving concrete change, but plenty of success in achieving shifts in the media narrative.
Moreover, what is immature about this? A temper tantrum? What makes you call this a temper tantrum? Temper tantrums are, by definition, uncontrolled. This is an extremely controlled and planned response. This is law we're talking about. A law that threatens these businesses, and, through them, their customers. But most of their customers have no idea this law is even in the works, or don't really get how it could affect them. What better way is there of telling them the effect beyond... Well... Telling them?
In a functioning representative democracy, there can be no more effective means to defeating a law than informing the public and getting the public to contact their representatives and inform them that there is a problem en masse. This is a means to achieve that.