It happens with Boney's also (Bonehilda, the maid from SN). I gave up on having a bar with her as all she did was drink, pee on the floor, mop it up, drink, pee on the floor, mop it up, drink, pee on the floor, you get the idea. Just out of curiosity I waited to see if she would stop when the house got dirty and things broke down. She didn't, she just kept right on drinking, peeing and moping.
Got rid of the bar.
I guess you could build a nice room for the bar, or have a half wall around most of it, leave a section for a door and then lock it to only household, that may keep the butler, or a Boney, away from the bars.
Have never tried it to see if it works.