There is a implied statement that cetaceans would somehow need to learn English to receive similar protections as people.
English? Where did I say that?
However, communication verbal or nonverbal that conveys agreement to participate in a society is a requirement.
This kind of communication would need to happen either individually or representatives cetaceans would need to come forward who could vouch for others of their species. From there, we'd need to observe whether or not the agreement(s) were being followed. This starts to sound silly, doesn't it? But that's what being a member of a society entails. That's what being "human" or reasonably equivalent to oen entails.
Why do they have to participate in our society in order to be protected from torture/murder/slavery/etc? The point of this article is that they have their own society and should not be made our playthings.
I'm also not sure why they would need to agree to some kind of treaty with humans just to be spared our cruelty. There's no evidence they mean us harm, we have the ability to protect ourselves if they did, let's just leave them alone.
Why do they have to participate in our society in order to be protected from torture/murder/slavery/etc?
That's a strawman. The proposal was to give Dolphins "the same rights as humans".
Protection of the creatures from hunting and physical exploitation is sufficient and something normally agreed to through international treaties. Equating cetaceans with humans is unnecessary and illogical.
No, the proposal is to give cetaceans the rights of life and liberty. Humans have quite a few other rights. Animals have no rights whatsoever.
The proposal is not equating humans and cetaceans. It is stating that cetaceans are close enough to humans that we should respect their life and not treat them a property. One hopes that an alien species landing on Earth would feel the same about humans...
This too will sound silly, but we don't even know if that would happen or could happen with Dolphins and Whales, because they've really just never been given the chance. It'd be like someone invading a new land they discovered, and just killing anyone in their way, without waiting to see if these people would indeed like to participate in their 'society'. But actually, on top of that, even if the dolphins could say they'd participate in this required society - why would it be deemed appropriate for the humans to make the rules here?
If you call something a treaty, isn't it expected to be discussed and agreed upon by both sides?
Humans have to make the first step and propose a first draft because of their current position of power. Unfortunately, cetaceans so far haven't taken time to try to learn how to communicate with humans. A treaty with cetaceans would be a display of pure goodwill, as opposed to e.g. peace treaties between mutually menacing powers.
Another interesting question is how many treaties are needed, since cetaceans are obviously no more unified than humans.