There is a way to have your cake and eat it too!
3 Steps:
1.) Open up the G.E.C.K. first... wait for it to load up... then pick Warrington Station out of the interiors list.
2.) Add the Ghoul Mask to a custom-made container. Lock it... and place the key upon Roy Phillips.
3.) Change Roy and his Gang from -good-... to neutral or evil, depending on tastes.
Now! Go Play!
The natural result of this change is that, if you want the ghoul mask WITHOUT the negative Karma... you can still get it. But if you -don't- care about the Karma... you help out Roy and his Ghoul-friends... and get -two-.
Of course, you could just script the quest so that it moves the mask from the locked container to his inventory.
Then it's just a matter of whether you want to be good or evil. As per usual for Fallout 3.