"gogogo" might make me quit this game.

[MaxCarnage]

And they are actively choosing to run in without the full party for whatever reason everyone isn't there. They could have chosen to make sure everyone was ready but instead they set the party up for a wipe with people missing. That is entirely on them.

If you are the healer, and you're not in cutscene, you should be ready, even if a dps is not. They ran in thinking that you were good to go, but you decide to be power hungry and try to play "god".

Not having a dps when you pull is not setting the party up to wipe. The healer refusing to participate because of their moral grandstanding is.

No matter how much you try and justify it, there is no justifying punishing people.

By the way, you choosing to not be ready at the boss is just that; a choice.