That first example was from a specific thread that actually happened when someone made a command-line tool, and the whole discussion was incredibly unproductive

That first example was from a specific thread that actually happened when someone made a command-line tool, and the whole discussion was incredibly unproductive and full of "look at me, I solved this eons ago, this developer sucks" messages. You're probably right there is a fine line between those two, but they are not identical. It's the difference between saying why you wouldn't necessarily use something on the one hand, and showing off while berating someone on the other. Asserting that a project's existence is unjustified is a bold and unfriendly claim. Saying that it's simly not for you is another matter entirely.