Are they paying customers? Good, GPL and commercial dual-licensing is a thing, and thank them for their business!
Are they people who would like to just use the software for their benefit, modify it to their taste and distribute, and keep the improvements concealed from everyone who made it possible? Tough luck, nobody promised them a free ride like that. They're still free to run unmodified GPL'd software.
Is there a third kind that I fail to recognize?
(Edit: added "and distribute".)
My theory is: the HN crowd that hates reciprocal licenses are developers who dislike that they can't easily use that code for work - that is, their employers makes it hard for them to do so vs. BSD-type code. They care more about developer freedom (to integrate various pieces they feel entitled to), more than user freedom (to modify the resulting software).
They aren't uncool, they just have terms that lots of people have good reasons not to want to deal with, and which many devs don't want to impose on downstream (in part because lots of people don't want to deal with them.)