More than that, it really makes me want to push it. It's made of gold!

Honestly IMHO the sensible thing would be not to show a Merge button at all, unless merging is an action that's available to the user.

e.g. at GitHub, when I can merge a PR:

And when I can't:

Note the merge button currently also hides "rebase" if enabled for the user, so it cannot just be removed (unless we move the rebase action elsewhere).

Which actually would be a good thing, because I had no idea there was a Rebase button inside the merge button! (Hey, I said it makes me want to push it, not that I've actually pushed it.) I don't think I'd ever have learned that, on my own.