I used to be. But that was a long time ago, and a few men ago too. There is no amount of great sex of "mostly nice" that can erase the fact that this person doesn't give any kind of credit to your thoughts or your feelings. A comment like you have reported here is an indication that he doesn't value your opinions. My grandmother used to tell me, to have a good relationship you have to be able to communicate as well as fornicate - and as lowbrow as her comment may be, it is true. Who cares if you care about politics or not? Apparently you were trying to be involved in a conversation with him or show some interest in something he is interested in. That's the part of the puzzle he should have noticed.
Take note if he does this all the time. You don't deserved to be demeaned or made to feel stupid or unimportant. You, girlfriend, should be valued - and if he can't see that, trust me, someone will.
L