Knockbacks in PvP

[Wiwiriri]

So ehm.

Seemingly you can just pop a knockback skill in Borderland Ruins and knock anyone off that you wish while they traverse up the dangerous path to the middle.
I tend to laugh at Karens but I feel like a Karen now, getting quite annoyed by it.

How is this a thing? How do I counter this (does surecast work?)
Obviously positioning is a thing but if the other 2 ramps are being used by the other teams, I'm unsure what to do in such a situation then.

Now I wish I had a instakill button.