I find it amusing (in a sad sort of way) that many of those who react most negatively to any idea of Ecclesial or Marian mediation have no trouble at all interposing a father/husband as ultimate mediator between God daughter/wife. Take for instance, the horror of some Christians at the idea of Elsie Dinsmore choosing to obey God rather than her father.
This leads me to suspect that it isn't mediation as such that is problematic for this particular group, but mediation between God and men (males). This becomes even more problematic if the one mediating happens to be personified as feminine (the Church) or actually be female (Mary).
Hmm. You'd almost think that I'd been reading one of those "radical feminists." Well, maybe, if St. Theresa Benedicta of the Cross (aka Edith Stein) counts as a radical feminist.