It is one breed of dicklessness to permit your woman du jour to date another woman, but it’s quite another to “be okay” with her boning another “man.” 1) Have some self-respect and 2) Be the kind of “man” who makes it impossible for a woman to want to step out on you.
The “man” who is incapable of maintaining the full-time interest of a female is usually one of three things: extremely bland in personality, extremely broke in bank account or extremely bad in bed. All you have to do as a “man” is have one of these three things going for you. If you can’t even do that, then it ain’t no damn wonder she got a wandering eye.