That’s quite a great way to frame the notion, but there’s one thing that I think you should be gone deeper into.
“radicals attempt to understand the root of the social problem” — where did you get this from?
Sure, “by the book” virtual every meaning of the word (except in the context of politics) refers to the fundamental causes, foundation or root of a situation.
But in practice there’s no inheret connection to “try to understand”. In fact, there’s little to do with understanding rather than acquiescing to a perception of what the fundamental cause is. Moreover, there are huge differences between fundamental causes and foundation of a situation. Eg: it can mean something in the line of originalism — sticking to the original definition of something (as in religious fundamentalism — instead of trying to interpret and understand the fundamental issues there, religious fundamentalism is understood as strict adherence to the doctrinal foundations).
Refering a bit to your Bernie example, you say that he saw the fundamental causes of an issue and thought of all-encompassing, holistic solutions. But that part has nothing to do with your notion of radicalism. The fact that you have a grasp on the root cause brings no obligation to have an all-around solution. For example, to reach general povery reduction you could have holistic policies aimed at several areas BUT you can also have specific solutions for the black community and then have specific solutions for each community.
Same goal can be reached in different ways. Also, in the particular case of Bernie, the problem with holistic solutions that don’t speak to individual communities is that it’s always difficult for people that seem themselves as a separate community to adhere to more generic solutions (“what works for others doesn’t necessarily works for us, we have specific issues that don’t fit with your agenda”). If you want to apply for something that transcends whatever racial, social, etc divides YOU MUST first address the divides themselves, otherwise you’ll need to target those separate communities.
IMHO that’s a big fallacy of American politics. Nobody’s really trying to bring people together, but it’s more of a divide and conquer. Black people are treated differently that whites, hispanics, asians, etc because it’s convenient. On the surface there’s some money thrown at social issues but nothing that would cement the idea that the community that matters are us as humans, rather than other arbitrary divisions.