Germany really needs to make laws about its dogs. There are no leash laws, no pooper scooper laws, and nothing prohibiting dogs from walking freely on their version of the subway. Someone forgot to tell the Germans that we build cities to keep animals and nature away from us. We are sheltered from it, and we build an infrastructure where we can thrive without the problems that nature causes us. We build houses to protect us from the elements, we build cultural institutions that are not hampered by whatever gets thrown at us. We build offices to harness nature for our benefit.
A city is like a laboratory. We are supposed to have full control of all the natural variables here. When we allow some of the variables to go unchecked we end up with a useless experiment. When we let nature go unchecked in a city we end up with crap that we do not want - literally. Trees are nice, but if we would just let them grow anywhere it would be problematic for the city. Imagine a tree in middle of a highway. We can say the same of dogs. Sure, sometimes we want them. Sometimes they are aesthetic or interesting, but they are too much a part of that part of nature that can be very annoying if left to itself.
It is for that reason that civilized cities do not allow the free roaming of animals on their streets.
Animals are autonomous agents. They have a will, and they are unpredictable. They are also not morally accountable, and they have the potential for doing great harm. (Need I remind you of the recent murder trial of that Lesbian in San Diego (?) who was killed in her hallway by a neighbor's dog?) There is no good reason why a controlled Germany can't have or enforce laws about dog restraining. There are plenty of laws on restraining people. There are laws about who you can vote for and what you can say and where and when you can say it.
There is of course no animal rights issues here. It is certainly permitted here to put your dog on a leash, it is also permitted to clean up after it. The issue is about weighing the needs and convenience of the people versus the thoughtlessness of dog-owners. When the latter gets priority, I am not sure.