Should the Tone Arm be Removed When Installing Cartridge?

Been doing it for decades and always considered the arm staying mounted as the third hand needed when the arm did not have a detachable headshell or removable wand like on the Graham 2.2 .
I agree with Lewn, more risk of damage when attempting to reinstall arm with cart mounted.

millercarbon, I am not certain of your intended message. Are you disagreeing with me, in that you think the tonearm should be removed to install a cartridge? I've never ever even considered doing such a thing, but if I did, I would then be very worried about damaging the cantilever/stylus when re-installing the tonearm. That to me is even a greater opportunity for disaster.

Right.

The preferred method is Scotch tape the arm to the rest, install the stylus guard, remove the cart pins, remove the cart, and then install the new cart, etc. 

To remove the arm, move it around, and mount it, all with a cartridge installed is borderline insane. 

But that's why I say consider the source. The source without a doubt was an audiophile. No one else could even think up such nonsense. Normal people have way too much common sense. Only audiophiles have developed their keen obsession of overthinking everything to such levels of absurdity.

Normantaylor, you could do it either way but here are the considerations. 
You do not have a removable head shell. You have a very bouncy suspended turntable and three bolts and the tonearm board is off.
IMHO it is relatively delicate work made more difficult with a moving target. I would remove the tonearm board with tonearm and lay it on a towel to put a new cartridge in. It is safer this way with almost no additional work. It might take a big two minutes if that to unbolt and bolt on the tonearm board. Do not try to manipulate the cartridge wires with your fingers. Use small needle nose pliers or tweezers. The pliers are much better and you can probably get one at Harbor Freight for $2.00.

During my LP12 days, it was anathema to stress the tonearm bearings. Along with the many set up rituals with the Sondek/Ittok, this was one of the most enforced dealers' rules.