I would have thought the more obvious scripture would've been Galatians 4:26: "But the Jerusalem above is free, and she is our mother." Although I really don't think Paul meant it quite like that...as in verse 24 he says, "These things stand as a symbolic drama; for these [women] mean two covenants." Contrasting the old Law covenant with the new covenant--that was the point. But the Society doesn't need to explain that because it only matters that the scripture says "she is our mother".
Given that it's at most symbolic, we literally can't love our spiritual mother; she's not an actual being or entity that we can love.
And I reiterate as was said above, Jehovah's Witnesses are not children of God! This is what they are taught! So how can they love parents that aren't even theirs? They're going to be adopted 1,000 years from now, though, so...way to go, Dad...trying to beat those child support payments, are we?
--sd-7