I'm American, but I've lived in Germany (Hamburg) for ~1 year, cumulatively. I recall most dogs being leashed, but at least a few not. It didn't seem to matter to me, because every dog there was damn well trained. In that year, I think can recall one instance of a dog barking inappropriately (to the mortification of its owner).

I remember one dog in particular, which was unleashed and running with its owner, who was on a bike. It would run ahead, staying on the correct part of the sidewalk, until it reached a crosswalk or corner, then stop and calmly wait for its owner to catch up and give permission to cross. I think one time (of the 3 crosswalks it was in view for) it got impatient and went back to its owner instead of waiting in place.

As a result, dogs are commonly (though not always) allowed in restaurants -- they stay quietly under the table -- and some other venues, which would be unthinkable in the US.

There's not too much of a point to this comment, just sharing perspective. I guess if anything it's that I wouldn't be so categorical about "if X, then Y, period".

It's exactly the same in Switzerland. Dogs are so well behaved I wonder if they are a special breed altogether

Your wording might be a bit harsh, but I agree:

Dogs need (outdoor) space. As a dog owner you carry that responsibility.

Having a garden to (mostly) take care of this seems obvious. If not, when using public space instead, it seems strange to expect others (wildlife, kids,...) to take this for granted?

That’s his point.