To get Bull to that stage, you had to go through multiple steps. You had to initiate the relationship with him to start with. He doesnt' come on to you at all. You have to flirt with him multiple times and jump through hoops to ever get him to approach your character in a sexual manner. After that, you have to consent during the act like three times. He shows you what it means to be with him, and then he gives you a very simple choice of being into it or not.
If you say that you are into it then you are roleplaying your character as being into it. It's consent. It's consensual. If you agree when he says this is what you need, then that is what your character needs and you are now taking on that role in a bdsm relationship. If you have a problem with your character being there, then that is your fault for putting them in that situation. Bull makes it very clear.
Also, Bull can tell if people across the room are sleeping with other people, and even know how many people they are sleeping with. He is extremly observant. When the game tells you that he can see what people need, you have to take that at face value. So if you consent to his romance and go along with it, then the game is going to assume that you are acknowledging that this is what your character wants, and Bull is actually right about your needs.
Some people do need things that are not available in a conventional relationship and recieve these things from people able to give of them in a safe and healthy manner, just as Bull does in the game. Iron Bull is a romance option for people to explore that. If it's not your cup of tea, do not take that out on the character. He is not inflicting anything upon the Inquisitor, at all. It's actually a challenge for a lot of people who are trying to romance Bull to get him to make the moves.
Do not villianize him just because you do not agree with the relationship style he offers after great pushing. If you are warned implicitly not to stick your hand in the fire, and then do, you do not villianize the fire as being evil for burning you, or declare that the fire is not able to offer something healthy to others.