An activist investor is a kind of value investor. "These assets are worth more than the market says - the discount is bad management. Let's buy the assets cheap (good value) and change the people who, as owners, we pay to manage those assets."
The idea that such an approach is anything but value and anything but completely normal and somehow rebellious and untrustworthy is quite weird and speaks to some kind of capture of highly paid management position by some kind of group of people. (I really hesitate to use the word "class" because these people might be a temporary alliance including the born poor and status challenged - the marxist "born to it" doesn't help the analysis much at all. Think the cool, sports jock table at high school).
As opposed speculator. "It's going up, i just know it." Or market makers, or technical analysts, or reading tea leaves...etc
Value investor suggests you have valued the assets and have reason for thinking they are underpriced. Shareholders own the company's assets. Managers are their employees and are not owned any more than any employees or indeed humans are owned.
Ackman is both. He is an activist in some of his plays, however, as can be seen through his publicly traded fund $PSH, most of his investments are long-term value investments which is also the sentiment echoed in his investor letters/presentations.
However, to the point of his SPAC vehicle - $PSTH, he has already stated in some interviews that he is not always looking for activist plays, and that $PSTH does not need to be one.
The idea that such an approach is anything but value and anything but completely normal and somehow rebellious and untrustworthy is quite weird and speaks to some kind of capture of highly paid management position by some kind of group of people. (I really hesitate to use the word "class" because these people might be a temporary alliance including the born poor and status challenged - the marxist "born to it" doesn't help the analysis much at all. Think the cool, sports jock table at high school).