I don't see any difference between this and, say, kill cows.
Also, the news piece sounds too desperate in it's attempt to appeal to an irrational emotional response. The author goes to the ridiculous extent of claiming that
"the operator intends to kill [octopuses] by submerging them, alive, in freezing water."
I mean, isn't "being alive" a key precondition to kill an animal?
- https://www.nhm.ac.uk/discover/octopuses-keep-surprising-us-... - https://en.wikipedia.org/wiki/Cephalopod_intelligence
I fail to see how this is has any relevance. The ethical or emotional argument of killing an animal does not depend on vague assertions over the problem-solving skills of said animal.
Meanwhile I feel your blend of arguments is terribly disingenuous for the way they avoid facing the fact that people eat animals in general and octopuses in particular.