I can certainly understand why this guy would be annoyed at having someone regularly pooping against his fence, but it isn’t exactly the crime of the century. now, is it?!
Also, there seems to be the suggestion that the runner is somehow targeting this guy’s home specifically but I very much doubt that is the case.
I suspect this girl just gets the urge to take a dump at around the same time every day, perhaps aided by the exercise she’s clearly doing. And this is an out-of-the-way spot where she thought she’d get some privacy.
Should she wait until she gets home to do her business? Of course, but who hasn’t been caught short at one time or another. Nature waits for no one.