I think it's more a thing of the limelight. If he doesn't lick the boot, he gets shut out of the capitalist media sphere, which makes it hard to get any electoral traction. And people like him are willing to sacrifice principles (if they ever had them) in order to get elected. They just either don't take into account, or don't care, that by doing this, they neutralize the effectiveness of their own political platform.

Bernie Sanders wasn't even radical and he got shut out and misrepresented to a huge degree.