Well, a large faction of the LGBT* crowd is not going to like this. Bisexual indicates there are two sexes: biological male and biological female. All of the trans*, queer*, and non-binary folks dislike those who call themselves “bisexual”. This is really a strange and, many times, contradictory grouping of people (much like the gays and lesbians really don’t care for the other).
Likely he’s a sex addict and doesn’t care which sex as long as he gets satisfaction. People saying their bi-sexual are just excusing their addiction.