Taxes don't lead to equality.
Sure. Nothing leads to true equality, if only because equality is impossible to define.
But are you saying tax policy doesn't matter at all? It would be ok to tax one segment of the population at 100% and others at zero, for no reason at all, and there would be no impact at all from that? I hope not. So therefore it's s possible for tax policy to be more or less effective, and/or more or less, dare I say it "fair".
The entire purpose of taxing capital (which makes more sense than taxing "robots" which is just trying to open up a new system of gaming the definition of robot), is if you are concerned about growing inequality, which Bernie apparently is. I think the fact that inequality is growing is a fact and like global warming, there are disagreements about the causes, how bad it is, and what/if anything should be done about it. If you believe believe it's a problem and something should be done then a wealth tax would be a reasonable start since currently tax policy in incredibly generous to the rich. Warren Buffett wasn't wrong when he said his secretary paid more taxes than he did. That's in absolute terms, not percentage terms. A first step would be starting to charge the rich any taxes at all!
Currently we have a situation where middle class people commonly pay 30% or more of their income in taxes. Then they pay an annual wealth tax of up to 2.5% in the form of property taxes, and that's not even on their net worth, or on their equity stake, but on the market value of their asset alone (an arrangement completely unprecedented among any segment with more favor). Add in sales taxes, car taxes, gas taxes, and down the line. Compare this with the super rich and poor who either pay no taxes at all or even negative taxes. This has no impact on equality?
Most wealth tax proposals propose taxing a small percentage, and usually only on net worth not asset value. That's already way weak sauce compared to what the middle class already pay. That doesn't sound catastrophic to me. They say it will harm the economy. Sure. So you have to explain why cranking the screws to the middle class exclusively, to the tune of 30-40+%, isn't also "harming our economy". It is, of course, like all taxes. Imagine the multiplied economic benefits of Joe America actually getting to keep, spend, and invest more of their hard-earned money. But the middle class is the segment with the least favor and ability to influence government policy, and that's the real reason...not because it's the preferred arrangement economically but simply because it's possible to screw them the hardest.