You're not wrong, but that sort of manipulation is illegal. I have no idea what caused the flash crash of Symantec stock today, but if someone had taken a large short position right before a news article came out that caused the algos to go haywire, you can bet your ass the SEC would be all over them (unless they're Goldman Sachs of course )
"Ah, you miserable creatures! You who think that you are so great! You who judge humanity to be so small! You who wish to reform everything! Why don't you reform yourselves? That task would be sufficient enough."
-Frederick Bastiat
-Frederick Bastiat