Sorry to hear about your boyfriend's immaturity and disrespect. But I am happy to hear that you had the guts to confront him.
Unfortunately, his problem is not one that goes away overnight. A person's speech declares the condition of his mind and his heart. If those words are coming out of his mouth when you're with him, it makes you wonder how he talks and thinks when you're not around. Either way, it's a sign that he has a long way to go before he's the gentleman you deserve. A gentleman would not only have kept silent about the other woman, he would pay closer attention to you as she passed by, so that you are all the more secure in his love.
But he's not there. I would guess that he was like this before you met him, and so you should have gotten to know him better before you starting seeing him. That way, you would have known his character (or lack thereof).
Now, just because he acted like that does not mean that he is going to cheat on you (with his body). But you can rest assured what's going on in his mind when he sees women like that in the future. Therefore, I would not cling to him. He could really use some time to grow up and get a pure mind.