"Keying your neighbors car because they have a nicer one" is not an analogy that works for anything here.
What is happening in NPM is not a car being keyed. There is a profit motive for doing this.
Perhaps you could say "Stealing 1 gallon of gas from your rich neighbors car to feed your starving children makes you an asshole", that's an analogy that seems to fit what is happening here, and an opinion I would disagree with.
IF you steal gas from neighbors car to feed starving children does not make you an asshole.
If you do it in a way to minimize damage.
If you come over and mess his whole car up in the process just because "he is rich" - that makes one an asshole.
The same with spamming NPM, OK I can understand they feel the need to earn money - but they are messing up something useful for others in bad way. They probably could still put effort to do many other things that would bring profit and would not mess up thing that many people will start loosing trust.
What is happening in NPM is not a car being keyed. There is a profit motive for doing this.
Perhaps you could say "Stealing 1 gallon of gas from your rich neighbors car to feed your starving children makes you an asshole", that's an analogy that seems to fit what is happening here, and an opinion I would disagree with.