'Rent boy' specificallly refers to male prostitutes having sex with other men. It's used to cause offense.
A particular element of that intended offensive nature is that it's about homosexual sex. It thus uses homosexuality as an insult, and is therefore homophobic.
There you go. I'lll also quote
@711's post again for your benefit:
It doesn't just refer to male prostitutes though, it's the lowest of the lowest of prostitute work, the worst type, which is the intended offensive nature. I don't agree that it's right to narrow that down to homophobia simply because ultimatily it involves acts of homosexuality. Unlike faggot, which only serves one purpose, the use of rent boy plays more on the sex worker, just as there's a reason women are called "whores" instead of "luxury companion"....This nonsense that people would rather use "gigolo" if the sex worker was the main bit is just weird, there's hardly a negative association when people hear gigolo. Though i can easily understand why the term rent boy isn't appreciated by anyone, and that people in the LGBT don't want it to be used, but i don't really see why the term can
only be homophobic. If the term was specifically about homosexual workers, then yeah, but it's not.
In terms of 711's post that you refer to, imo he hardly clarifies anything. Yes, it's about sex workers that cater for gay men, but that doesn't mean that a name for those sex workers has to be homophobic.
But hey, if the vast majority only interpret the use of rent boy as an attack on homosexuals, then by all means, i'm the odd one out.