Hi, I'm Tim. (Excellent from Windia) :)

Again, ksing is never ok.
There's really nothing to discuss about this.

Lying is never okay either.

if we want to get pedantic about this, kill stealing is the act of rushing in and dealing the finishing blow to monsters that someone else did the bulk of damage to. It is not killing monsters in a map that people have claimed as their own. No one ever has "ownership" of a map anyway.

Perhaps things would have gone better if you had truthfully explained the situation to him instead of brusquely saying "we're full".