I'm not a fan of Halsin but I'm not sure what the problem is with him in particular. The game is rated mature and characters can be creeps. In fact, most of the characters in BG3 make creepy unwanted advances like they're somehow incapable of reacting to cues and navigating social situations. The game seems very "horny" and sex-obsessed in a way that comes across as immature and frankly just unsexy (something that is to be expected from a game that leans into its sex scenes for advertising). Thankfully, you're not forced to interact with that though.
All the other ones will eventually reach a key point where you can say you are not interested and they will not pursue it anymore after that. Halsin is the only one that continues to pursue it, in an even more creepy and disturbing manner, after you have made your rejection clear to him (and he has confirmed that he has understood it and that he will respect it).
