Again, technically you are correct. However, you are living in a dream world if you think that anyone who has a parent that is Jewish, is not considered 1/2 Jewish, whether you like it or not. That's just, realistically the way it is. Regardless of whether you consider this to be purely a religious consideration rather than a secular one. I don't mean say this with any negative connotation, just how the majority of the world considers it.
People don't speak of secular Jews as not being Jewish because they don't practice the Jewish religion or only their mothers are Jewish. They are still considered Jews, even though secular. I don't think there's much point in arguing about what I think you know is obvious. It's not a case of asking you to like this definition of Jew, it's just asking you to acknowledge that this is the way most people think, which is most consider Jewish like they would consider Arab, or Asian, or some other enthnic group. By usage, the term Jewish is looked at not merely in religious terms.
you can consider it any way you like. But, if you don't mind, I will use the same definition that I have used all my life. Whether people consider him 1/2 Jewish or not, I couldn't care less. From a religious perspective, which is my perspective, he isn't. So if you want to erroneously refer to him as Jewish, knock yourself out. You may as well refer to him as 1/2 bovine, because it is equally untrue. But far be it from this Orthodox Jew to get in the way of your definition of Jewish.