The xz utils shenanigans is a great example of both why open source shouldn’t be implicitly trusted and why open source allows for anyone to see the shenanigans and get the issues resolved/warn people.
If this was proprietary, it would have been near impossible and taken much longer to discover.
My humble opinion
Example
Locked in google services. DNS so google sees the sites you visit, tracks what you click, where you go, who you talk to, what you like, what services you use, where you spend your money, etc.
Freedom - no log encrypted DNS, no tracking, no surveillance and profiles stored that are gladly shared with whatever other company or gov dept that wants it. No blobs or beacons. The ability to see what is happening, to choose what to allow or disallow, to be able to edit, modify, clone, fork, etc based on your needs and wants. Not the Almighty profit margin.
Freedom to choose poison or antidote.
Another eg.
Nothing to hide may be true for now.
But what you believe need not be hidden, may, by some future government (or dictator), be deemed a crime, or worthy of retribution.
Allowing an unaccountable, unverifiable, monolith or shady actor is asking for problems.
The less data you share (or is unknowingly siphoned off) the less data you have to worry about being leaked /breached.
If someone you don’t know knocks on your door, do you let them in and make themselves at home?