if they manipulate the market downwards my investment. is worth less. I'd buy a stock long term for dividends. But since dividends are apparently rare these days (something about the evil of double taxing), we're forced to invest in the hopes that somebody will believe it's worth more later. What used to give stocks some worth was they value of the dividend, that you'd reinvest, to compound over the long term.
Without dividends, I think you should just invest in currencies. It's just as volatile, and you don't have to lie to people about the nature of the marketplace.