Roger's opposition may be motivated by a general dislike of doing anything societally-changing for reasons of climate (just a guess), which he reverse-projects as other people using climate change to advance their own social goals. (Although that charge against others does sometimes have a grain of truth.)
As for Romm's opposition, it appears to be that population control alone can't solve the problem, so don't bother with it. Only the first part of that argument is correct, and the second part is used against many partial solutions that people find inconvenient, like wind power or (possibly) nuclear power.
As for me, my interest in per-capita emission allocations creates a political reason for paying attention to population. It also means being concerned about international migration. I think some resistance on the left to population issues comes from revulsion against guilt-by-second-hand-association with some vile racists who've seized on population and border control. It's the racists who are the problem, though, not the population and immigration issues themselves.
A final note - recent increases in fertility in Northern Europe will make emissions control more difficult over multiple generations, if the trend continues. I see no reason against the reverse argument for reducing fertility elsewhere.
Bonus blogging: fantastic new pictures of geysers on Enceladus. There could be frozen microbes shooting out on those plumes - we just need to grab some and bring them back.