Is it safe to clear out a garbage disposal with a hand?
It would be up to you to decide the value of your hand.

I rather enjoy having my hands, so I use a stick when needed. Never felt the need to buy a specialized tool. Sometimes what's jamming the garbage disposal is, itself, sharp - a tin can lid or glass object, for instance. Naturally, those things are not supposed to be in there, but it does not mean they can't be in there, by accident. It's also a fairly nice place for growing things you probably don't want to get in a scratch, much less a full blown cut. So, even if the thing is unplugged or turned off at the circuit breaker, there's a hazard - if it's only turned off at the wall switch, there is always at least some potential for it to be turned on with your hand in there, and that would be rather unpleasant - but some folks don't want to bother making sure it can't be turned on, because they are sure it won't be...