I don't think having an Incubus trying to "hit" on a male character would be problematic.
Man on man seduction doesn't need to revolve around sex. A man could tempt another man with power, luxury, friendship.
A large part of the vampire mythos hints at homosexuality being more prevalent among them. Vampires are nigh immortal; boredom can easily lead to "trying new things", but that's the tip of the iceberg. Vampires are powerful, and lonely. They would be attracted to each other as rivals and partners. In the Ann Rice books, it's quite common for straight vampires to practice some seduction on mortals or other vampires.
In a similar vein, an Incubus could tempt a male character promising him sex with women. "Come with me, and we'll have all the women you can dream of".