However, forcing a debate and a likely filibuster is a conventional partisan politics and the fact that this option was not exercised suggest a tactical error, even for the POTUS who is risk aversive. In other words, they could have acted differently even within the political constraints imposed by the "zeitgeist" as Republicans in their place would - but they did not. And this is inexcusable.
As to your point about mass mobilization - please keep think in their proper perspective. A couple hundreds of thousands protesters yelling and stomping their feet poses zero threat to the establishment. Just look at France where the protest were proportionally much larger than anything that the US saw since race riots - they had virtually zero impact on the political establishment.
The elites were never particularly fearful of protests - typically the riot police could handle these very effectively - but they are even less threatening today. Mass mobilization and protest can work only when it can tip the balance of power in the political establishment - e.g. when two opposing factions have more or less equal power, and mass mobilization in support of one can give that faction extra leverage. But that does not obtain in today's political climate. The elites seem to be remarkably united that capitalism is the way and that there is no alternative - the major bone of contention seems to be who is going to manage the capitalist economy. And that is not going to chance because of protest actions. Again recent protests in France, and other EU countries provide painfully clear examples of that.
Wojtek