What flippant attitude? The part where they tell the poster to just read the source code? That's not flippant that's the exact answer to the question. If you don't trust it just check out the source, it's all out in the open. If you don't like it don't use it, same as the telemetry alsame as the desktop. FOSS is about choice, you can choose to use Gnome or fork KDE and remove the telemetry yourself. Or maybe just flip a switch and turn it off.

Edit: Also the whole argument about how the "average user can't read source code" is useless. Remember when audacity put 'actually questionable' telemetry in their code? Everyone was up and arms about it, distros still don't provide the new updated versions of audacity in their repos. Now imagine that with KDE, it's a much bigger project, any average user would figure it out with 5 seconds of reddit or a simple google search.