The US should vigorously and publicly support the notion of democracy and human rights. That is not to say that the US should somehow intervene to bring democracy to X or Y. Every case is different and in MOST cases the US would do well to do nothing rather than doing something stupid (those seem to be the only choices allowed by the state dept and pentagon in many cases).
Every case being different, the case in Egypt right now is that the US should publicly press for democratic reform and should work behind the scenes to have the army kick out Mubarak and install a functional interim regime and open up the media and phones and so on. That would be best for the US in every way. To work to "stabilize" Mubarak would be the height of folly...
US policy makers have spent so many decades propping up dictators and being afraid of democracy, they do not seem to be able to let things go a little...if they do, they may be pleasantly surprised at the outcome in many cases...and they will not do worse than they are doing right now in almost every case.