Seizing the assets of convicted criminals is not controversial because we see that as part of the punishment and/or restitution.  It's the rampant abuse of the process on non-criminal American citizens -- those whose assets are seized before guilt or innocence is determined whereby LEO divvies up the haul between the local, state, and feds -- that is controversial.

If you screw up, you pay.  If LEO screws up, you still pay.