While it's wildly misquoted on the interblags, you can't read out the word "essential." The point of the quote isn't that no trade-offs between freedom and safety are appropriate, but rather that we shouldn't trade away those freedoms that are "essential." It is debatable whether monitoring of the internet, a technology that didn't even exist for most of American history, is a trading off "essential" liberty, or whether its an "inessential" liberty.
Ben Franklin, like the other framers, realized that freedom versus security was a trade-off. Remember, the Constitution itself was a reaction to the Articles of Confederation, which created a government that turned out to be too weak to protect peoples' safety, both from external threats (Indians, European powers) and internal threats (domestic insurgents). The Constitution draw the safety versus freedom line a little closer to "safety" by creating a more powerful, more centralized federal government.
This balancing is also why the 4th amendment uses the wiggle word "unreasonable." Searches and seizures are okay, just not "unreasonable" ones. Well how do you decide what is "reasonable" versus "unreasonable?" You figure out how to appropriately trade-off freedom versus security! If the founding fathers didn't intend for us to engage in such balancing, they would've left out the word "unreasonable." No searches and seizures, even if necessary to solve a murder or kidnapping. After all, that would maximize freedom at some cost to security.