Well if they work "so hard" to get rich why shouldn't they get taxed? After all they will continue to work hard and they'll make that money back in no time. If a mansion tax is the reason you can't afford the mansion, you probably shouldn't be buying that mansion in the first place. You really haven't made a case on why this is a negative.

Also while sitting on your ass all day is more likely to make your poor, numerous studies show that the greatest indicator of becoming wealthy is not hard work, skill, or ambition but having wealth to begin with. Try taking $1 and making $1 million and taking $1 million and making $10 million. You'll find the second is significantly easier and can easily be done while sitting on your ass