Place some thin cardboard on a cement floor and drop the hub flat on the cardboard a few times and the bearing will push the seal outwards. You may need to drop the hub with a bit of a push to get it to move.
1crosscut Done that before. Works almost every time.
So basically you kneel on the floor and hold the drum/hub assembly about waist high and drop it so it lands flat on the cardboard. The weight of the bearing coupled with the inertia from the fall will push it against the backside of the seal that is in to far pushing it outwards.
This technique is often used to remove the bearings completely.