I second this.
Crossfit is a high impact, high quality workout. That being said, when getting back into shape, focusing on a base fitness and building an aerobic base will enable him to get more out of those high intensity workouts at a later date.
People that don't CrossFit should be hesitant of telling others whether or not CrossFit will work for them. I've seen people with a "base fitness" from body sculpting, or having completed P90X multiple times, come in the box and get smoked because they didn't have the cardio or the strength they thought they did. Whether you're a high level athlete (like some NFL players) that has turned to CrossFit, or a complete newbie to fitness, the workouts can be tailored to meet your needs. If you're at a box with coaches that don't encourage this behavior in order to make sure each member is getting proper training, they have bad coaches and you should find a new place to go.