Hannah Arendt in her most famous television interview after the Eichman process said what shocked her in 1933 when the Nazis came to power wasn't that the Nazis came to power, it was how many of the people she preceived as friends and allies, especially in the intellectual space would convince themselves with fantastical theories about why Hitler being in power might be a good thing actually.
The truth is that many people are cowards and even more people are just small-minded. The problem of the "I have nothing to hide"-excuse is that it shows thst this person has no concept about how their small personal ideas would affect the world once you roll them out in scale. Not only that but it shows that they haven't understood how power is organized in their democratic societies.
Let's say we would have nothing to hide and we give up our rights to the people we as the voters are meant to hold accountable. Even if it is a benevolent government filled with honest actors, large scale surveillance has the problem that there will be false positives. Surveil 360 million people each day and with an totally utopic accuracy of 99% and you still get 3.6 million false positives a day. In reality however these processes are much less accurate and the people who use those powers much less benevolent and honest, e.g. it is not uncommon that police look up their exes, spouses, people they personally hate etc.
The biggest problem however is that we have a division of power for a reason in democracies, and the people who vote giving up power in order to give more to a government is bad actually. Democracies need to be designed in such way they can survive one or two governments that try to abolish that system. Giving them a "spy on everybody" -power coupled with let's say secret courts is a good way to risk that form of government for generations who then have to fight bloody civil wars and revolutions to get the power back.