I think you can simply point out that if the protocol was open, beyond bot development, if users could choose their clients, and searchable plain text archives

I think you can simply point out that if the protocol was open, beyond bot development, if users could choose their clients, and searchable plain text archives could be made available, etc, all but the most political detractors in these arguments would be appeased. But the thing is, that will never happen, because we are not talking about a protocol, but a service. And that to me is just the whole problem. There is just nowhere to go, and people who try to develop in this space are squashed by the TOS. At the end of the day you can either be fine with the lock in here, or not.