I'm more inclined to agree with Tyson: while the rover(s) were great news and certainly generated exitment, if a manned landing had been done at the same time, *no-one* of the large public would have even noticed. That is to say: manned missions will *always* generate more excitement than robotic missions.
But, don't get me wrong, I'm all for going to Mars too, and I think purely as a PR stunt (though gathering enthusiasm of/from the public is worthwhile) it's not worth its money, unless you open it up to the private sector and get the economical factor playing. But I just wanted to say that the public, politics, economics, etc. and, indeed, science, all play a part in any decision NASA takes.
It's never going to be one sole thing. Some people - scientists included - will think one thing is a pity, while others think another things is wasted money. For instance, as one can see, some scientists are against manned spacetravel, because it cuts in the available budget and thus it means less science for them. Purely from the premise and viewpoint that NASA is there for them to get scientific data, I can understand their complaints. But I think they're mistaken, when taking a more global approach. I think taking steps to actually colonize other planets and become a multi-planetary species is important too. But everyone has his opinion on it, I guess. Politicians see NASA as a means to have and keep jobs and employment in their region, for instance. That's not a worthwhile or useful goal in my book, but I guess politicians see it differently. Etc.
Anyway, I wish they wrote into the constitution that NASA gets a minimum of 1% of the GNP. :-) That way, things would become less cut-throat, and NASA would be assured of stable finances, allowing to plan long-term.