Golf is not a sport.
Golf is not a sport, shooting is not a sport, and Chess And StarCraft are not a sports either.
To understand why I am saying golf is not a sport you have to understand the way I classify what a sport is.
A sport, in my mind, needs to contain two components: a physical one and a skill aspect.
There are many activities that have only one of those two aspects, either requiring skill to do well, or requiring some form of physical talent, but fewer of which fall into both.
Golf does not fall into both categories. It does without a doubt require skill to be able to well, as there is no way a beginner would be able to outdo a pro without practice, but that doesn’t imply it is a sport. Where golf is lacking is in the physical skill, training, endurance, and outlook on exertion. There is no way you can argue that golf requires high level physical training because it is completely possible for an unfit person to be a golf pro, and they do exist.
The problem is exemplified by the fact that it is completely acceptable to complete all 18 holes using a golf cart to get between holes. What would people think if marathon runners took a shuttle bus part of the way? And while pro golfers don’t use carts they do have caddies who lug all their gear around. This practice doesn’t help to dispel the idea that it takes not fitness training play and do well.
One way golf could be improved to bring it closer to being a sport would be to include some form of time constraint. Say you have one hour to complete the course, and then players are scored based on some combination of time and the score they managed to achieve in that time. Better yet, start 4 players at the same time (having completed some form of qualifiers) and then after each hole reshuffle the groups according to points gained in their heats through the time/shots/placing rating system.
All in all golf is not a sport because it lacks a physically strenuous aspect, fosters an atmosphere where fitness is sidelined, and those who consider it a sport are either too naive, too lazy, or have not been exposed enough to real sport to be taken seriously on the subject.