This thread has degenerated into right / wrong camps, ignoring the fact that many instances fall somewhere between the two. The simple matter is that any real professional will listen to relevant information, no matter what the perceived source.....
Back in January I was SLF on an AC Jazz flight from T/Bay to Winnipeg. The a/c had been de-iced, but was delayed due to slush-clearing from the runways. From my window seat just behind the left wing, it was clear that snow and ice was reforming on the control surfaces during the intervening 20 minutes.
When the F/O announced push-back, I called the cabin attendant, informed her that I was a private pilot (20 years on bush planes) and asked her to advise the flightdeck that there was a visible fresh accumulation of snow/ice on the control surfaces. She called the flightdeck and within 15 seconds the FO announced there would be a very short delay while the a/c was de-iced again.
Should I have kept my mouth shut as a 'courtesy' to the flight crew? Maybe we would have been fine, but why try and save 5 minutes in this world to arrive decades too early in the next? I think this shows the crew considered third-party information for something they could not themselves see, judged it relevant and acted on it accordingly.
Everybody won.