Bear, maybe be a little less cynical to the point that you could reference a different scripture. Matt 12:46-50. The larger point is that saving faith in God puts one into the family of God. Abraham obviously had it. I think the “grandfather” part could be used figuratively as an extension of the metaphor that Christ already used, but can’t be a dogma of itself (which kind of usage was a problem the early church had). Why not clarify the sphere of its validity, then go on. This is almost like quarrels about words. There are important doctrinal hills to die on. I fail to see how this is one, if it is.
The “mother of god” concept is purely a pagan concept. It is vitally important as Catholics base much of their belief system on it. Not admitting the separate fully human and fully God aspect of Jesus causes a total lack of understanding Matt 12:46-50 as well.