If think it depends on what you're trying to focus on, as an amateur musician I wrote most of my best stuff while I was together with my ex. I can understand why people working their spiritual side might choose to separate them selves from the opposite/same sex, but if you're trying to be creative I think it really helps to have someone who causes you really strong emotions.
As far as most people who are considered geniuses being gay; I think it depends on their field of work. It probably is true for creative geniuses involved in the different forms of art, but probably not the case for geniuses involved in scientific fields.