Delta-V costs are not the only criteria.
The number one limiting factor of any space vehicle is cost per kg at launch. NASA could build a Mars vehicle any size they wanted except they have to figure a way to get it in orbit without spending the entire budget to launch it.
Irrelevant when the number one defining factor of STS is how much pork can be siphoned off to spend into each supporting senator's district and not whether or not it helps the an extremely improbable Mars mission or even just the improbable "planned" moon flyby.
You're the one proposing that it is "easier [to] refuel at the moon" [sic] so the onus is on you to detail how much developing a moon base
I am not proposing. I am relaying what has been proposed.
We're not in junior high here, you can stop trying to play semantic games. You bring the subject to the conversation, you defend it. Knowing that there is hydrogen on the Moon does not mean that it is under the form of water ices nor how accessible it is nor how difficult and expensive harvesting it may be.
sufficient to perform extraction of fuel/oxidizer and the means to transfer them to earth launched vehicles are versus doing so from earth.
No oxidizer is required for electrolysis.
You cannot know that lunar hydrogen is in the form of water ice, have not proven it's accessibility, have not proven that you have worked out the process to develop it as a usable ressource nor proven that you can do so for less than it will cost at that point in time to deliver from earth. Pray do so now.
Don't forget that spending billions to develop a rarely used infrastructure is precisely the point that most critics of NASA have at present...
1) I didn't say it would be easy. I said it would be "easier".
Proof? Nah you don't have proof (indeed you _cannot_ at present) and if this post is any indication you'll try playing semantic games again to attempt to avoid answering.
2) How much fuel is left in a space vehicle after Earth orbit is reached? Very little. There's a reason most space probes use gravity assists to speed them towards their destination. And being unmanned they don't have constraints on time and resources that manned missions will have.
Oooh, ooh I know this one! it's because Nasa, being hobbled by the U.S legislature never invested significantly in lowering the cost of launching mass to orbit, preferring to spend the money on futile studies as the only meaningful yardstick became $$$/district.
3) NASA has been directed to do something; you may not like what they propose but that doesn't mean they can refuse to do it. Get to Mars is directive. For NASA that means getting to the Moon again.
You seem to have been living in a cave with no contact with the exterior for the last few months. Allow me to enlighten you: Nasa's congressional masters and the president have changed. No-one knows exactly what the implications are yet but Trump's declarations that cost cutting is more important than rockets to nowhere means that the directives are to change soon and Mars is not likely to be a directive for much longer.
"Current" NASA plans have a tendency to change with administrations.
Engineering and numbers don't change with administrators. Math is math. What is the cost of launching directly from Earth vs launching from the moon.
Spoken like someone who lives off of studies that will never come to fruition.