Who can I romance as an evil male dwarf?

Actually I think a person is more likely to be in a relationship with someone who does things they don't approve of than be friends with them. How often does a person get into a relationship because they are attracted to the other and when they discover what they are really like, persist because they are either besotted with them or have the romantic notion they can change them. Why do people stay abusive relationships despite what their lover does to them,  irrespective of what their partner does to other people?

By contrast whilst a friend may continue to be loyal up to a point, they are less likely to be worried about jeopardising their relationship by being honest with their friend if their actions disturb them. If the person persists with such behaviour I think they would actually find it easier to walk away than a lover would.

In both cases, if the person was aware of the behaviour before they became close to the person, then it is likely it would never happen, although I know of a very tragic case in my own family where someone had been warned about the true nature of their potential lover but went ahead because they were convinced they could be a good influence on him, only for that not to be the case and paying for it with their life.

However, if I understand Iddy correctly, it is more a question of whether his dwarf could credibly be attracted to the person given the way they present themselves to him. This is why I have suggested he might be more attracted to Iron Bull or Josephine initially because overall their outlook seems closer to his own. It should be remembered that the Inquisitor is offered their leadership role immediately on arrival at Skyhold before any of the romances begin in earnest. There has already been time for the companions to get an idea of what kind of person you are by your behaviour up to then. If they really do not approve of you, then your approval will remain low and the romance will never get off the ground.

Clearly the way the romances are presented in the game it would seem they continue once they have started regardless of what you do. By this I mean once the romance is locked in. Clearly if you do something in the personal romance quest to alter their opinion, like killing the merchant in Dorian's romance quest, then that will end it but thereafter it is only the Inquisitor who is able to end it. With some romances it is not possible to end it at all once you are locked in. I believe the only exception to this is Sera, who will end it with Lavellan if you do not say you are going to abandon your culture entirely for her, which to be honest is something I feel that Lavellan should have realised would be a sticking point before starting the relationship but, as I say above, may be they thought they could live with the criticism and Sera would learn to tolerate their beliefs. Anyway that is not going to be a problem for a male dwarf.