Interesting thread. After reading it through, I *think* that the the original post is sarcastic, and meant to spark exactly what it did, a debate. However, it is also very difficult to express sarcasm (as subtle as it is) in an online forum. I'm sure there that people here have been equal parts offended, angered, curious and amused. I find it thought-provoking.
As humans, we are unique in that we have a conscience. Humans alone have the ability to reason aside from instinct, to distinguish right from wrong based on their individual morality, to have an emotional response to our experiences, and to identify that response as emotional. It is just this that gives us a burdon of responsibility for all living things. All living things deserve dignity, respect, and compassion. And while these are concepts that only we humans understand, comprehend, and either embrace or disregard, it is still our responsibility.
All animals feel pain on some level - physical pain. It is physically painful to die from shock, or poison, or a parasite that slowly eats away at your body. It is less painful to die quickly, by falling asleep/losing consciousness (freezing). Emotional pain is something unique to humans, but not physical. And to come full circle, often when we recognize a lapse of our respect or dignity towards those we are responsible for, we experience this emotional pain -- guilt, remorse, sadness.
Whether a fish lives for 3 seconds, 3 minutes, 3 hours, or 3 days in the sewer, or septic, or pipes, it is physically painful, stressful. Whether we are talking about a $50 fish, or a 19 cent fish, whether it is treated with $20 medication for 3 weeks or $1 of aquarium salt for 1 week, it deserves to be treated with respect and dignity. If $$ is the argument, freezing the fish is more economical, as you do not pay for the water you flush, nor the clove oil to euthanize. If convienence is the issue, why not throw it outside? It will die faster out of water than in the toilet.
If we lose sight of this responsibility, lose sensitivity to other living things, ignore our impact on those around us, for good or bad, we lose part of our humanity.
And doesn't that bring us even closer to the fish we say we are so different from?
(now I'm going to get some chocolate milk!)