1. Those who intuitively understand power dynamics and endeavor towards a "don't kill, and don't be killed[0]" mentality, even if they understand that the radical change they want is generational
2. People who want to wear the boot
To be clear, every organization and movement has #2. Libertarian conservatives are chock full of Trump bootlickers, neoliberals were basically completely coopted by corporate bootlickers, Free Software activists have an unsavory habit of falling in with whatever RMS says, anarchists have to deal with people who want to break windows for fun, socialists have "tankies" that just want Soviet Russia to invade and oppress, etc.
The book "The Tyranny of Structurelessness" covers this tendency if you want to read more.
It's called "pragmatists versus theologians" (or fundamentalists, depending on the translation), and it was extremely common in any left wing movement in Europe from the '60s to the '90s.
Umberto Eco wrote a fair bit about it. it's not exclusive to left wing movements but historically has been very apparent in such groups[1].
In short, You got a group of people whose main objective is to improve the condition of their community and it's inclined to bend the purity of their message in order to achieve some realistic objective (to the point sometimes of fully betraying the original ideology altogether)
And then you got a group of people whose idea is that philosophy trascends their or anyone else life, and the point is the fight itself. As an italian song of the '70s cynically puts it (very loosely trasnlated) "The fight has to be endless, comrade, otherwise I won't be a general for the people anymore."
Truth is, you need both of them to make a movement capable of actually going somewhere, despite ironically having in itself the main cause of its own collapse.
There's much more variety, but it depends on what you call radical. There are stances which are radical in the eyes of the general public which are not violent, nor revolutionary.
I read it as saying they are making the same kind of error rather, than a direct comparison. My subjective impression is that the poster is wrong on the point about RMS.
1. Those who intuitively understand power dynamics and endeavor towards a "don't kill, and don't be killed[0]" mentality, even if they understand that the radical change they want is generational
2. People who want to wear the boot
To be clear, every organization and movement has #2. Libertarian conservatives are chock full of Trump bootlickers, neoliberals were basically completely coopted by corporate bootlickers, Free Software activists have an unsavory habit of falling in with whatever RMS says, anarchists have to deal with people who want to break windows for fun, socialists have "tankies" that just want Soviet Russia to invade and oppress, etc.
The book "The Tyranny of Structurelessness" covers this tendency if you want to read more.
[0] There are a lot of Floweys out there.