Many a time I have wanted to tear my hair out due to other's determined ignorance towards horse riding. Most often we riders are disregarded and thought more of hobbyists... but I guess anyone who plays golf can relate.
You see, whenever I am asked in class to reveal any sports I partake in, I always say this: "Cross country, track, and horse riding." The last figure seems to warrant a few laughs... and an evil glare from me.
So, I've decided to break it down. I've chosen something that is a hobby and another sport to compare horse riding to. I believe the results shall surprise you.

First I shall go through the hobby: writing. It is enjoyable, calming, and obsessive. Most of the time a short story becomes a trilogy... but can horse riding relate?
Horse riding is fun to participate in, and, depending on the rider and mount, calming. So, one and a half for the point of hobby.
On to the sport... I've chosen football, as most Americans can relate. In the sport of football, there is an incredible amount of focus involved- you space out, you lose. Also, working out and running are essential to build up the required muscle to compete and do well. Then there's the addition of scoring. The more points you have, the better you win.
So, for horse riding: Focus is a tremendous part of this activity. I've known people who have broken bones and narrowly avoided surgery just because they spaced out for a little while. Then there's working out... yeah, horse riding requires this as well. If you don't work out, you risk having an inadequate supply of muscle and falling off (or having your horse run off with you). Neither of those are fun.
But points... I bet you're thinking, 'She can't possibly relate horse riding to scores!' But if you are, you're wrong. In my riding association you earn points when you place well. In the class you're participating in, the points will build up over time. At the end of the showing season, there is a fanciful banquet in which the winners receive rewards.

So, horse riding (when put through that simple test) seems to match up much better with the term sport. So, the next time you go about telling we Equestrians it isn't a sport... you'd better have on your running shoes. Trust me, we really don't enjoy being skimmed over.