I'm an insensitive jerk

So I come out of the stall and a guy in a wheelchair rolls up and shoots a sarcastic, "Try to be a little more sensitive next time." What did I do that was so horrible this handicapped individual would consider me an insensitive person? Let's take a journey:

As many of you know, I'm finishing up a bachelor's degree in graphic design by taking evening classes at the Art Institute of Portland. I usually get off of work around 5pm, hit the train, grab some food and barely make class at 6:00. This particular evening I was running a little late for Advanced Illustration and the only food place that is directly on my way to school is Baja-Not-So-Fresh. I knew we were having peer review in class, so I'd be able to munch quietly in the back without any problems. So I grab some chips and guacamole and slide into my seat around 6:05. The teacher was late so I was home free.
I sit quietly in the back, giving feedback on fellow student's illustration work and munching happily on my chips n guac. Round about 7:30 we take our first break of the evening (class runs until 9:45) and at this point I'm starting to feel a little tickle in gut. By the end of break I've got the sweats, you know when everything on your body is sweating, even places you didn't know had sweat glands. That's my first clue that something is horribly wrong and I know at some point in the evening I will have to take care of exorcising the demons currently posessing my innards. But I try to be a champ and head back to class.
Not 10 minutes in to class el Baja Diablo tries to take control and I make a b-line for the one restroom on the entire floor. I bust through the door like SWAT at Mike James' house on a porn raid and look for the nearest stall to perform my Exorcism. The first two are taken, leaving the handicap stall as my only option. Not wanting to call janitorial to clean up a mess I happily accept my new accomodations and even secretly appreciate the handles installed next to the commode. I settle in, open my mouth and begin praying loudly to the porcelain gods to excorise the Guacamole of Doom and send it back to the sewers from whence it came.
In the meantime the other 2 stalls had finished their business (or been scared off by mine) and vacated the bathroom. Keep in mind I mentioned my exhortation for relief was extremely LOUD. No doubt other people could hear and knew what was happening as one kind gentleman asked if I was OK and offered his deepest sympathies.

Around 5 minutes into my little seance and I hear an obviously annoyed voice ask, "Are you going to be long?"

"I hope not," is my reply, followed by more prayer and supplication

He angrily responds "Why did you have to choose the handicap stall when the other 2 are open, a**hole?" at which point I realize this man might possibly be handicap and need the stall I'm in. I reply as politely as I can between vomiting "The other 2 were taken when I came in." I finish as best I can, clean up and exit the stall. Sure enough, there is a pissed off hesher in a wheelchair who shoots me a menacing glance. Being a nice guy I try to apologize to which he responds. "What the f*** were you thinking? Try to be a little more sensitive next time."

It took every ounce of energy left in my body not to grab him by the mullet and puke all over his ball-point-pen-band-logo emblazzoned jean jacket.