Well, simple. It's a war. "If it's red, it's dead"/"If you're blue, fuck you"
You can expect this on all PvP enabled servers, and if you are flagged on non-pvp servers too.
Though I don't see the gain of killing something with 1 hit, but I laugh when a high level fails to gank a low level. It's a small border.
In the end, some view it as the ganker having low skills and others see it as troll.
I accept ganking on one condition, that the ganker accept being ganked himself/camped/farmed. I've seen many that suddenly rage if it happens to them, I take delight in hunting gankers and killing them in fun ways. (Engineering ftw)
Just remember, main importance, if you like doing you better accept being a victim too.