The “If we tax billionaires, they will leave” argument is like saying “If we make murder illegal, then all the murderers will leave”. It’s flawed in a number of ways. But I’ll highlight one. We want them to leave. They don’t contribute to our community. Instead, they are a succubus. They rent apartments and don’t live in them. They prevent us from building the infrastructure we want. So GTFO if you don’t like it.