Let's Dispel with this fiction that...

[SillyAmerican]

I care about values and policy. Clinton is the epitome of the establishment; Obama was/is a sell-out; Cruz is gonna be a religious tyrant. I'm okay if the Democratic party crumbles; I'm okay if the Republican party crumbles. Sanders and Trump are running campaigns based on principle, albeit very different ones.

I second the above: So?

Agreed.

Both the anti-establishment candidates, Trump and Sanders, have no business running within the party structures that they're in. They are doing so simply because the way things work today, to be a viable candidate that's taken seriously, one must run within one of the two major parties.

To echo what others have said: So?

[SillyAmerican]

If your values are not shared by most, it is a road to permanent losses. US constitution forces a two party system: that means both parties have to be grand coalitions of disparate ideological factions. Sanders is incapable of leading such a coalition. If you want an ideologically homogenous party to matter, you need to change the Constitution: at the very least you would need the Congress to be elected by some sort of PR.

Why do you believe the U.S. Constitution "forces" a two party system? I can't figure out how you reach that conclusion.