People who cry market manipulation tend to be people who are just plain awful and picking stocks and need an excuse as to why they're down 30% when the overall market has gone up 10%.
Being pedantic, every buy and sell is manipulation to some degree, as you're sending a signal to other buyers and sellers in the market. Somebody who owns a large shareholding in X can manipulate the share price by selling or buying large quantities of shares for example.
Insider trading is the largest risk, and, obviously, has and always will happen - but it doesn't move markets.
Disinformation, information fraud, etc., all of that I agree with. HF trading being able to provide arbitrage... well I don't really see that as manipulation, that just sounds like someone else better at the same game as you. And trading algorithms... I don't have any loss of love for these, so outwitting an algorithm is spoils for the victor.
Here's some *legitimate* market manipulation I can get behind: share buybacks. I'm not sure I see how holding a large volume of shares otherwise creates manipulation, but I guess that might fit. So then, manipulation?
**ok, people like Jim Cramer are obviously using their platform for personal gain, I would put them in the "manipulation" camp, but not sure how large his flex may be.