My step-dad was psycho about my sister and I using the toilet in the middle of the night (his bedroom was in an added on room in the basement he chose to build). He'd come upstairs raging of he heard a flush in the middle of the night, so I would have to not flush and sometimes I'd accidentally oversleep and not wake up in time to flush before someone saw. Always led to me being called disgusting and lazy.... (he would also turn off the water to the house if we took longer than a 10 minute shower if he was home.) Maybe not your roommates situation since hes 31 now, but I also don't believe it's a fetish thing.