Right on

Actually, if the package describes an entire day's intake it may be right on the money. Combine 1500 calories of lethargic waking day activity with 700-ish calories of sleep and the body will achieve neutral balance with that diet. It's actually unhealthy to diet (for long term effects) by cutting the nutrients to your body and remaining inactive.

Sure. Just because they're on an elliptical trainer doesn't mean they have to be going all out like everyone else. I've seen plenty of fat people at our gym on the elliptic machines and treadmills just slowly moving along. But that's what matters most for weight loss - 65-65% target heart rate activity for long durations. The guys in the Army's weight control program that lost the weight the fastest (and longest) were the ones who were required to walk everywhere all day rather than simply run two extra miles at the end of the day.

But if the person is so obese that it's not possible for joint pain - then 20 minutes is better than not going at all. They just need to follow it up with something like an exercise bike (even less impact) to maintain that heart rate for a little bit longer to benefit from the exercise.

I have to disagree with your points:

1) If you have an active job ('blue collar') then 2k is reasonable. Sure, if you pilot a desk all day, then 1.5k is probably more realistic, unless you work out a lot. Also, remember that different heights and builds change this quite a bit. A very lean me is 6'3" 200 lbs, where my step brother at the about the same height (6'4") is only lean if he gets down around 165 lbs. We are both athletic, but in different ways.

2) Yes, a fat person can do 50 minutes on an elliptical trainer every day. They will not have it ratcheted up all the way, but since they are larger, they get equal calorie burn with less speed and resistance. Sure, there are some that are so morbidly obese that they can no longer walk without becoming winded, but these are the extreme minority. For most, it is a matter of persistence of what you can do, not ability to do something extreme.

When advising my students (that want to lose weight outside of karate) on how to lose, I normally suggest that they watch their favorite show (to distract) on the tread mill, aim to be exhausted (high heart rate, heavy breathing) during the ending credits, and then bring the treadmill down a light pace for at least another 15 minutes. This plan normally takes some endurance training to reach, but most get there within a month, and the effects on their health is very noticeable.

As someone who struggles with weight, I find the most important thing is a lifestyle change, not just exercise or reduction of intake.