At what rank should Soldiers be exempt from organized PT?

No one should be exempt.

Lead by example,frigging never.

It should never be based on rank. It should be based on results from your fitness test. If you perform well above average, it shows that you probably exercise outside of command PT. For most of those people, command PT is more of an annoyance than beneficial. However if you constantly score at the bare minimum to pass, that shows that command PT is probably the only time your exercise and your just a few push ups/sit-ups or seconds from failure. That happens at all ranks. Doesn’t matter if you’re Captain Crunch, if you are “just the minimum” kind of person, you should be in formation. Not showing up and everyone knows you’re a fat body shows your junior personnel that people in the upper chain can cut corners just because of rank.

As a former Sailor and Military Police, I think that it is imperative all, and I mean ALL, active Military members from full birds all the way down the ranks be involved in organized PT. The best work outs my received is when our C.O. would show up at crack of dawn to PT with his people. It shows not only a concern with his/her subordinates well being, it also shows that no matter what your rank, physical fitness, and "operations ready" is a priority for everyone.

Marine Corps - Lt Colonel and 1st Sgt / MSgt
Army - Lt Colonel and 1st Sgt / MSgt
Navy - Commander and Sr Chief
Chair Force - Who cares. They're not real military anyway.

ZERO!

E-9. Other than that they should be with troops and lead by example. Yes CSM’s could doPT with troops at their choosing and of course on all unit runs etc..

None. Regardless of rank a military person should be fit. Granted the older they get the requirements should listen but they still should be able to run a mile without killing themselves

I actually have dual service experience both with the Army (enlisted) and the Air Force (Officer). I learned my leadership from the Army as junior NCO (Sgt-E5) and consider this training the most important training I received in my entire career.
I was always taught that a leader leads from the front whenever the mission permits. This in my opinion would encompass PT. I vividly remember during Basic Training when the Battalion commander came out and did a run with his troops. His action lifted morale showing that PT was not below him and that if he could do so, so could we Pvts.
As an officer I always did my PT test with my Airmen. I always told my NCOs' and Airmen I would never ask them to do anything I was unwilling to do, had not done in the past or would not do in the future. I like to think that my performing my PT with my Airmen solidified this statement.

CSM R E Howard (Ret.) There is an expectation of a fitness level one should expect and require of a all soldier's. As a solider, I need to know you got my back, which means you need to be there to have it.
I think you could have some some incentives in place for those who go the extra step and max out their PT test. Only come to group PT once a week, only take the PT test every other time, allow to attend MFT course, etc...
Everyone should attend large organizational PT events for morale.
Senior Officers and NCO's (LTC and above, E-8/E-9) should be able to choose what group PT events they attend, keeping leading by example at the forefront.
Keep Jesus first and "Be fit to fight another day"