Are lockdowns justified?

[Ranjr]

Sure, if humans weren't humans, lockdowns may very well work. But humans are humans, and so lockdowns have little or no effect. And, when discussing politics, we must not forget that humans are humans.

I don't think this explanation is correct, as the same is true for countries which had no lockdown, such as Sweden:

people don't gather inside as much in the summer

And you don't think lockdowns result in people gathering inside secretly? If so, they are counter-productive because humans are humans.

We shouldn't try to describe a complex situation with a few simplifications

But that's how science works. Science builds simplified models of reality which can actually be used to make predictions. A model that is too complicated to make any prediction is not science.

The lockdown does not force people to secretly or openly break it.  In fact, when people act rationally and abide by the protocol, the protocols work.  So there we have our difference in point of view.  You blame irrational behavior on a rational measure.  I blame those who act irrationally.  

I don't understand the significance of the graph you keep showing.  It reminds me of climate change deniers who wait for a cold day to say there is no global warming.

The more complex the model, the more accurate.  The more forcings and factors taken into account, the better.  Take gravity, since it's handy.  By your opinion, Newton's and Einstein's gravity would be science, but quantum gravity would not be because there is as yet no complete and consistent system.  Yet, quantum gravity is science because it is falsifiable.  Einstein's gravity is more accurate because it is more complex.  Also, you haven't built any models here.  You have made unsubstantiated claims about grocery shopping and vitamin D.  Who doesn't roll out of ICU or a nursing home, whether in a chair or on a gurney, having been deprived of sunlight?