It's gotta be something deeper than his opinion on a certain type of woman. Even if that opinion hit you somewhere personal. Often we are unconscious of the reasons we are or are not attracted to someone. Opinions change. People evolve. People adapt. People rarely feel 100% about an opinion they talk about, and that opinion may very well be something that they say due to where they are at emotionally. It could be something that points to a greater sense of entitlement in him. It's often a variety of unspoken things that lead to a loss of attraction. If the straw that broke the camel's back was indeed about his views/preference of women, I'd suggest you maybe look into why that statement triggered very defensive feelings in you. What kind of threat did his statement pose to you? Did it strike somewhere deep inside you, do you associate a part of yourself with a certain type of woman he said he is not attracted to?

If I were you, I'd just call it off as they say above. Short, sweet, generic wording. Don't go crazy and say you're a lesbian. And don't tell him why. After all, attraction is weird, and people's preferences often change over time. Attraction is a lot about where you are at at the time. It's also based on schemas and ideas we have about the world and people that exist in our mind and are contingent upon significant figures in our lives. It's a very complicated thing and it just makes no sense to hurt him and say why you lost attraction to him, because you probably can't tell the real reason and much of it may about about you and what is going on inside you. Just say the usual "you're nice, but" and cut it off. Then maybe do some soul searching.

Studies show more women are fluid in sexual orientation than men. Men's sexual orientation tends to be a black and white thing based on sexual attraction whereas women's is very based on emotional connection. According to research, women may have phases in life where they are attracted to the same sex, but often it's about the relationship they have with the specific person, be it male or female, and the sense of security, closeness, and attachment they have with them. And this goes back to models of attachment developed throughout the earlier life stages where the brain was engaged in development and pruning. If you're in therapy, maybe explore this with your clinician. The development of sexuality often goes back to your childhood. In any case, you can use this event as a catalyst to becoming more self-aware and discovering what you really want in a relationship at this point. Hope my advice helped- the advice on breaking it off was a bit obvious, but I wanted more to point you in the direction of looking at this in a long-term, analytical perspective.