Upvoted, and thank you for the explanation.

I'm never going to live that one down, am I?

If it helps, I didn't even remember that one of the times I've called someone out on "X is crap" was you. So consider it "lived down".

taken aback at your assertion that it doesn't contribute anything.

You're right. How about an assertion that it doesn't contribute anything that couldn't be easily rephrased in a much better way? Your example of "Don't use this thing for this purpose", especially if followed by a brief explanation, is an order of magnitude better than "X is crap", and I doubt it took you more than 5 seconds to write.