In what way is it selfish to either dive without a buddy, and/or to set clear boundaries at the surface as to what assistance you will or will not provide on the bottom?
If we both have an hour+ deco obligation, our respective dive plans called for us to each carry our own deco gas/safety reserve but no more, and just before beginning the ascent you have a catastrophic failure that costs you your gas... how is it selfish for me to do the math in my head and tell you to follow your plan, rather than compromising my own? If you want to argue that it's irresponsible or morally wrong to set up such a dive plan in the first place (and I suspect you team divers would, given your gas planning approach), so be it. But nobody is having the rules of the dive sprung on them for the first time at the bottom.
Would I do everything I could within the boundaries of my reserves and plan to get you as far through deco and up the line as I could before sending you on your own way? So far as I could safely do so, of course I would. Would I insist you switch back to your own gas and take your chances once I calculated that the risk to my own safety was too great, and fight to protect myself if you were too selfish to follow your own plan? Yes, I would. I hadn't realized that DIR's philosophy included the tenet that two chamber riders/bodies were better than one.
As an aside, your legality comment is as ignorant as it is unnecessary and pointless. Ignorant, in that no U.S. jurisdiction requires a private citizen to put themself at risk to rescue another unless they directly and proximately cause the crisis in which the other finds themselves. One may not untie a trespassing boat from one's dock in a storm -- life and limb trump property rights -- but the gas for one's dive is not an issue of property rights. Unnecessary and pointless, in that there's little chance of any reliable evidence of what happens on a dive reaching the surface and, in any event, the last thing anyone would be thinking about in what is a self-defense situation is 'gee, is this possibly a tort?!'
while I agree that two chamber rides are not better than one. I do believe that two chamber rides are better than one fatality.