Lives, Fortunes and Sacred Honor.
Not that we have any fortunes left, and the lives that could be forfeit would be those of slaves, were action not undertaken.....
(If not now, then when? If not us, then who?)
As if there were a question as to the time of the tipping point, this article should set to rest any doubts about the urgency:
http://www.freerepublic.com/focus/f-news/2295381/posts