Knowing it was a 10 year old scottie makes it a little funnier, but the rest of the details are unimportant.
We can deduce everything else. The owners usually take him out through that door to the yard periodically and one time they weren't there. The scottie holds it in, and holds it in, until he can't anymore and then he has to decide where his ass is going to be when the shit comes out, inside which he knows is wrong, or he can take his chances on the screen door.
It looks, in that moment, with the breeze blowing through, like all that shit might just magically fly out the other side and land in a neat pile. Those are tiny holes, shit goes through holes, so maybe, just maybe....
Thinking about this story now, and having felt like the scottie quite often in life, as I've found myself pushed and pulled in so many contradictory directions, I see it as a pretty great thought experiment for describing categoies of people.
I know, for instance, a lot of people who would find the scene of the poop in the screen door and the ashamed scottie and enter a rage, "How dare he! He knows better than that!"
If the dog would talk, he might say, "but I just couldn't hold it in any longer, and you didn't come to open the door, and-"
And this person would respond, "Excuses, excuses, excuses" or something equally reductionist and infuriatly dim, absolving himself from his obvious culpability. And in further meetings with higher ups the story would eventually evolve until it was simply, 'that ancient scottie just shits on things."
In a lot of power dynamics, this sort of thing isn't just allowed, it is the way business is done. Problems that the higher ups don't want to deal with, minefield tasks, for instance, get delegated to people who everyone knows probably can't handle them, but at least they might clear the beginnings of a path.
This is horrible for the scottie and new employees at a company, but really just another crass methodology of the modern corporation. What do you expect, didn't you know you were just a pawn?
I contend that when you find yourself in this kindof ambush, that you always immediately protest at that moment, vociferously and with pointed sarcasm.
Say "No. That's not what happened. You didn't do your job and that was the necessary condition for this mess, not my bowwel movement. This is a team effort unless you want to put a door handle down here, and you failed your team, so shit happened. Own up to it you douche."
Of course they will fire you, because they are lazy and cowardly, and can't stand cognative dissonance.
I contend however, you want people like this to fire you, otherwise you'll end up living in their upside down world where everything is your fault and it's only a matter of time before they make you fall on your sword so they can have a more pleasant picnic.
Professional life is the search for a team that won't fuck you over(and maybe you will be rewarded for your work, actually, imagine that!).
Once you get fucked over at a job, they are no longer any part of your professional career and you are free to move on without looking back. You have bigger fish to fry.