I know SS men who weren't comfortable participating in mass murder could transfer, or in some cases simply refuse. But could they actually choose to leave the SS altogether without facing persecution? How difficult was this?
I suspect such a thing would have been impossible, aside from deserting and fleeing.
I say this as this would likely have been considered a violation of the anti-sedition decree 'Zersetzung der Wehrkraft' or 'Wehrkraftzersetzung' ('subversion of the war effort' or 'undermining military morale').
Objecting to the duties or orders given to an SS soldier would have likely been considered an opposition to the Nazi ideology.
Source: The Oxford Companion to World War II covers Wehrkraftzersetzung as well as its extension to civilians in 1939.