The God of the living or the dead?

The SDA Bible Commentary comments on Matthew 22:32 (the parallel passage to Mark 12:18-27): "What honor is there in being the God of dead men? Abraham, Isaac, and Jacob were dead at the time God appeared to Moses before the burning bush. Why would God identify Himself as the God of the patriarchs, except in anticipation of the resurrection?" SDABC vol. 5, p. 483.