Isn´t that the non consensual option ? (I´m letting the redlight district and the gloryhole aside) but you are given the choice to shut down the males as far as I know. (redlight district is clear if you work no much option there and gloryhole is the fast 100 buck´s butt this is more or less free will if you want to do this) there will be always a percentace of hetero sice Alex had a boyfriend back in her hometown.
Hetero for Alex : Glory Hole (avoidable, but usefull to gain money and for the Mistress path development), her first boy friend, the biker (avoidable), The masqued rapist (avoidable), The truck driver (avoidable), The man in the laundry (avoidable), Ryder (avoidable), Broom (avoidable), John (Ash friend, avoidable), The Sancho worker (avoidable)...
In fact, hetero sex is nearly all avoidable, but it's impossible to decrease the hetero desire below 5/10, so Alex remains automatically bi.
Additionally, an important part of the game is lost if you avoid sex with males