In the occasion that the upper connection of the hose, where it connects to the hard line, is corroded to the extent where the 11mm nut rounds off while attempting to remove the line you may need to clamp the 11mm rounded off nut in a pair of locking pliers in order to get enough of a hold on it to break the lower 14mm nut on the soft line free.

In this case you'll use the locking pliers to hold the 11mm nut while backing the soft line off of it.

You may find that it is difficult to remove the hose in this way as the soft hose begins to twist. You will be working against the twisting motion of the hose this way. Since you are replacing the soft hose anyway, simply cut the hose with a suitable pair of wire cutters or a utility knife.