Besides cosmetic reasons there is no point to secure your base with barbed wire ingame. The item itself is useless. Nobody is using them.
Problem: You are able to to dismount it from outside the base.
Solution:
Change the mechanic ingame. Allow dismounting them only from the back.
Build a Fence.
Attach and build barbed wire to it.
Go to the other side of the fence (the front / outside).
Use pliers to dismount.
It also doesn't help that you can target and dismount the barbwire from few feet away from the fence ... meaning if you would build the fence behind a chain link fence for example (from which you can "target through"), you can dismount the barbwire even if you aren't close to it.