Ok, not a bad idea to tax loans...but now you're taxing people buying a home, car, financing a repair on something, etc. The point is to tax people with massive wealth, not to target someone like me who had to take out some financing to pay for a home heating boiler replacement. You could use a "well, except..." argument, but then I could counter with the same slippery slope argument you use later in your reply.

A wealth tax actually discourages investment through stocks

Why? Stocks are still the biggest way to increase wealth without lifting a finger to do any actual work. Maybe you get taxes more, but you're still making more money. You mean to say they're so greedy that not making billions fast enough would cause them a fit of pique? What else would the uber-wealthy invest in? Why not grow a business instead? They could also simply find a workaround to not take loans based on assets, boom, suddenly not collateralized. Enjoy your personal loan.

I disagree with the baseless slippery slope argument because you stated income tax while arguing retirement accounts. They are not the same thing, and that's why we're having this discussion.