You wouldn't have to believe that there was any chance of keeping that language in the bill. But it's worth noting that the full bill including the states language passed the Education and Labor Committee, where the only Democrats to vote against it did so for unrelated reasons. You wouldn't even have to believe that the state single-payer language (which was added by amendment in the Education and Labor Committee) could possibly work with the rest of the bill. I've heard that claim but not seen evidence for it, and in fact the amendment allows states to completely opt out of the rest of the bill. You'd just have to lobby Pelosi, Hoyer, Waxman, Miller, and Rangel to leave it in there. Three of them are from the state most likely to enact single-payer first, California. And the Californian in charge of the issue, George Miller, did vote against it in his committee, but it passed nonetheless; and Miller is himself a cosponsor of HR 676, the bill to create national single-payer. In return for lobbying these leaders, you might find you had major new support for what you're doing on the public option.
I address this advice both to activist groups and to the Congressional Progressive Caucus, which has not yet supported the state single-payer language as strongly as it has the public option. Supporting both involves no contradiction whatsoever, and could unite your constituents. Remember, this is not creating single-payer in any state. This is simply leaving states the constitutional right to provide their constituents with healthcare.
It Takes Two to Tip the Balance
While proclaiming healthcare to be a human right, you can also work with Congress to get a few more humans their rightful healthcare. You wouldn't necessarily have to believe that any of the bills we've seen thus far meet the standard. You wouldn't have to believe that a bill that did meet your standard is likely to emerge at all (in which case a single-payer bill is very unlikely too). You'd just have to acknowledge that a serious partial step would be better than nothing, and communicate better that lobbying for the ideal outcome is often the best way to reach a better compromise than can be reach by lobbying for your bottom line. Let your fellow activists know you're on the same side and helping to reach a better compromise by creating a position to compromise from.
Now, I know that I've been saying all of this, in more or less the same words, for months. I know that getting the state single-payer amendment through is unlikely. I know that getting a useful public option or even a token and pointless public option is unlikely. I know that by this point we've all offended each other on top of having disagreed with each other. I know we're all frustrated, out-spent, disorganized, and pulled by our own parochial interests. I know the media sucks. I know that sooner or later we're all going to die.