The trouble with Sanders is he's hardly the most radical person ever. Unlike say, his right-wing equivalent Ron "Happening" Paul (who genuinely had notions radically different from his party). pretty much everything his mouth wouldn't be too out of place in the DNC national platform. He is merely a sexed up Clinton wearing antiestablishment clothes. With that in mind, his rabid fandom acting
- as if Sanders is "the only politician speaking the truth", (I can name at least politicians people saying the same stuff) and throwing everyone else under the bus. I actually find this really creepy, if I'm honest.
- act as if presidency is equivalent to the DPRK's Supreme Leader. No there's no point in primarying incumbents; or even building a more progressive coalition at the state or local level; no just elect our magic man to congress and all our problems will poof away.
- talking with lame, dorky catchphrases like "feel the bern"
- flooding all criticism (or even non-glowing coverage of the man) with hysterical accusations of being part of teh anti-sanders conspiriceh.
Yeah, Clinton is infinitely worse than Sanders, but I'd take her fanbase over the cult any day.
Sanders is a lot more liberal than Clinton on a lot of issues. Iraq war, Syrian war, TPP, fracking, Glass Steagall, and so on. There are significant ideological differences.
You are correct that he's not the most radical person ever. He's more conservative than the frontrunner to be UK Labour party leader.