An “impolite no” is not just a ‘no’, and it’s the latter that was required and not the former. He could have ‘recommended’ that the whole patch-set be re-architected to avoid depending on the proprietary module. There was really no need (or any excuse really) for being so coarse.
>need to be more polite about rejecting low quality work is puzzling to me.
First, it's not low quality
Second, for sure you have to be polite if you don't pay him (but even when you do, you should)
Third, imagine a 16yo get smashed like that (not that i say he is) and what a devastating and demotivating thing that could be...welcome to the linux world
Overall, those Superstar Linux dev's are mostly ignorant borderline autistic assholes who can't develop a good Filesystem like XFS or ZFS from scratch, then moan about Nvidia, but work on a computer with around ~100 proprietary systems called firmware. One accusing the OpenBSD peoples for being masturbating security Monkeys just to say (4-6 years later) that they where right (a super rare occasion for a linux super star). You know what i like to say? FUCK YOU LINUX, FUCK YOU GNU (but not grep...gnu grep is nice)
As far as I can see, if you have to say "no" doing so politely has no downside, whereas behaving like this clearly has some.