Of late, there are lot of news in mainstream media and news on Wall Street getting into BTC. More of a good news though, but still I am afraid if they will look to manipulate and crash the market just like what happened with recent China instance.
I doubt that they can crash bitcoin to its knees when there are a lot of investors coming across the globe. And the crash due to China was not as result of manipulation, they really have to dump bitcoin because their government is putting a hard stance on it.
As for manipulation, very difficult, it should be a coordinated attack. And for the institutional investors coming in, they are much very welcome to enter, they have a lot of cash to pour into the system which is good news but manipulations? I doubt that they can pull it that stunt.