Tom, I do not think it is appropriate for you to be posting your fetish material here. This is a respectable family website.
However, since you asked, what’s funny is not the sharting per se. It’s the fact that you have no sense of humour about yourself. You take yourself way too seriously, and you like to portray yourself as being better than everyone else. You can’t admit to any fault. You come up with all these grandiose claims about how special you are, how important and influential.
Yet it’s blindingly obvious to everyone but you that this is all nonsense, that you have wasted your life and all that raises you above the ranting wino on the street corner is the roof over your head. You fail at everything you do, invariably in ways that are of your own making.
If you merely failed, that would not be funny. Failure of your own making, yeah, that’s kind of funny. Failure of your own making while you try to act like you’re this infallible bohemian genius who’s better than the rest of the world? That’s hilarious. Wounded dignity is one of the oldest jokes there is, yet it never ceases to raise a laugh.
You shitting yourself is funny because it is about the most undignified thing an adult can do, in direct contrast with your pomposity and self-importance. The more you try to salvage some dignity, the funnier it gets. You’re a classic comic archetype.
Seriously, though, adult diapers. It’s more dignified than shitting on the floor.