It should be about banning pathways to become a billionaire by:
- rent gouging
- price gouging
- price fixing and monopolistic behaviour
- land banking or other hoarding behaviour
- rent seeking (increasing your share of a set value without producing anything new)
- underpaying workers
- cheating workers out of overtime and holiday pay
- privatising what should be public services (health care, prisons, basic infrastructure)
- tax evasion
- bribing politicians to enact favorable legislation (sorry "lobbying" and "campaign contributions"
- externalising the environmental and social costs of doing business
- committing fraud
- inheriting obscene wealth from your parents - which I would define as "the amount any human requires to meet their needs without working a single day in their lives x4". Let's say $50 million in today's dollars.
Nobody is "against" billionaires because they can imagine being one themselves one day but everyone is against the things listed above and, let's be honest, that's how 90% of billionaires became billionaires, not coming up with some brilliant, innovative idea that changed the world. The people doing that are the engineers whose stock options land them, maybe, in the low hundred millions if they're super lucky.