OK, moral reasons aside, it is a waste of money to just keep buying plecos, grow them out and then kill them, over and over. The b***h doesn't care about that because it isn't her money being spent.
Morally I think what she does is wrong, buying a fish only to kill it when it becomes an inconvenience. It is only a garbage eater to her, an excuse to not clean her tank, and not really a pet. Whatever. I dislike the woman for other reasons, the way she treats her tank is only a tiny part of that.
I've always wondered why she doesn't just A: buy a bigger tank to properly house the fish she tries to cram into her 20 gallon or B: buy a pleco suited to life in a 20 gallon that will actually eat algae (her reason for buying them) such as a bristlenose.
We all have killed fish in our tanks at sometime or another, on purpose or not. We've put them in the freezer when meds don't work, had them get bullied to death by poorly chosen tank mates, had them jump out and dry up on the floor, boiled or froze them from heater failure, poisoned them when using a garden hose to fill the tank, forgot to add the de-chlor, cut off their heads and eaten them, oh and don't forget the feeders some give to their big monsters (feeders are still fish!); you get the idea.
I guess it's like this: you don't want to kill your fish, don't. But we can't FORCE other people to stop killing their fish, all we can do is express our OPINIONS.