I think what Mad Max said is completely true...
Peoples stomach and wallet are the bottom line. If you are feeding someone, and paying them well (and their family), they will overlook just about anything. Of course, abusive behavior negates this, but....
If you think this is wrong..consider...
You probably hate your boss...
Why do you keep working for him?
Hello
Quite true. Your magus just have to think about what he does in the lab. Hint: don't dissect corpses ,eat babies or worship obscure gods. This of course only apply if your lab assistant have some conscious.
Happy hunting
/Max
I dont thin my boss is an inhuman monster that would damn my soul.
Hum...aldoth me personly might think it was cool if he was. 
Hmmm... Considering that envy is one of the emotions caused by The Gift, a non-gifted lab assistant would appear to be a prime target for infernal corruption. I could very well see them being granted the False Gift (oh boy! oh boy! oh boy!) or some other infernal powers, leading to not only their own ruin, but that of the magus they worked for, by association. 
Ah, you like the False Gift? I agree, that's a very cool story hook you have there. 