Hi,
It's generally a nervous thing - they were right in as much as he probably is getting ready to poop or pee on you if he feels any more frightened or stressed.
The good news is it should happen less and less the more he trusts you and gets used to handling.
To help with that it might be a good idea to restrict handling slightly but that depends on how often you handle him at the moment and for how long each session?
Doh!! I type too slow these days.
dr del