How do I delete a route from Linux routing table

with the route -n command you'll obtain

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         192.168.178.1   0.0.0.0         UG    0      0        0 eth0
0.0.0.0         160.98.123.1    0.0.0.0         UG    600    0        0 wlan0

sudo route del -net 0.0.0.0 gw 192.168.178.1 netmask 0.0.0.0 dev eth0

you'll get all parameters respectively from above

The types of the routes with the ! flag are either unreachable or prohibit. route, being an ancient utility from net-tools, does not differentiate between the two. Use iproute2.

The net-tools way to delete these routes would be to use route del on it. However, net-tools provides no way to differentiate between the rejected route and the other one (because the dev argument is optional, though not specifying a device is likely to remove the unreachable route).

iproute2 allows you to do it like this:

ip route del unreachable 10.1.0.0/24
ip route del unreachable 192.168.46.79/32

It might not be unreachable, but prohibit. Use ip route with no arguments to determine which.