Gamblers add liquidity, which is better for society than them hiding in a basement playing cards.
Stocks are essentially ponzi scheme financing. They have all the hallmarks. Then often literally use the cash from sales of stock to pay dividends. Most companies will never pay dividends, though, so the idea for a purchaser is to hold on and cash out while it's big before everyone else does.
Fraud is the worst when people have an expectation of trust, assuming they're protected by regulators. They never are. Madoff. Bre-X. Enron. Even highly regulated markets are always riddled with fraud. People should expect the market to be riddled with fraud and act accordingly - it keeps the populace wise.
Regulations are an attempt to get something for nothing which always just ends up with a bunch of friction, corruption, barriers to entry, and lawyers.