I thought endorphins were suppose to make you happy?

For our sixth week in a row, we tackled sprints at the Tan today. But we had a bit of an odd experience and every time I think of it, I get more and more angry.

The short version is that a crabby, old man yelled at Penny and I for standing in his way. (We were in the normal spot that everyone stands in.) Since he perceived that we were in his way, he got in Penny's way when she was doing sprints and wouldn't let her pass. (Tim is re-enacting the encounter in the picture.)

Who does that?
Why isn't he happy he is outside and burning calories?
It makes me want to commit to being happy to exercise.