I'm not intending this as a point for or against this patch, but I reading this set me wondering how many of the other assumptions we'd normally make about Bitcoin would still hold given this (fairly reasonable-sounding) idea that a majority of miners will be acting purely out of economic self-interest, regardless of damage they might do to the Bitcoin ecosystem.
I reject your premise. The health of the bitcoin ecosystem is hopelessly intertwined with the self-interests of miners. This relationship goes in both directions. Bitcoin cannot survive contrary to the self-interest of miners, and miners cannot survive without the common good of bitcoin.
If it turns out that the bitcoin system does not ultimately align these two forces, it does not deserve to be continued
The good news is that bitcoin does not appear to contain this flaw. The people that are damaging the ecosystem are those that are advocating and defending practices that are unsafe and cannot be made safe, such as accepting transactions secured by hope rather than work.