Speculators are heroes. All good things come about because of speculation. Just as Ron Paul would say, demonizing speculators was bad when the Emperor Diocletian did it which led to famine just as it is a bad idea now.
Bernie Sanders is a talking about a transaction tax. That is the worst idea on the planet. That would cause mass suffering. Traders create liquidity which is a big part of what creates the valuation companies. A transaction tax would make it much harder for companies raise capital and it would cause capital flight out of the company. A reason Wall Street is so successful is that despite its problems it is still the best place in the world to park money because we don't have as many taxes and regulations.
Here is what happened when Sweden implemented one in 1983. Their stock market immediately dropped 8% and it ended in a depression 8 years later when they got rid of it. It is an evil, immoral tax not on evil financial people, but on everyone. Read up and stare into the abyss that Bernie Sanders would cause.
https://en.wikipedia.org/wiki/Swedish_financial_transaction_tax