Well, sir, I yield to your superior knowledge - though I do wonder what the "appropriate data" in this case might be. My guess is that airport and airline policy on apron trash is pretty clear - any amount greater than zero is too much.
So I'm puzzled that the tone of your response seems both dismissive and defensive. Experience has shown that observation - even casual, amateur observation - has a value in flight safety. It's observation that leads to the thought "maybe we should keep this area clean" or even "maybe I should pick up some of this stuff before some paying customer thinks our standards are slipping."
I'm not suggesting UAL is unsafe. But whether you operate one flight or a thousand flights per day, how you do (or fail to do) the small things invites assumptions about how you do the big things. Smart airlines know this - and so do their employees. Just in the hour I was watching, at least a dozen staff ignored an obvious accumulation of FOD. That doesn't look good - and I'm surprised anyone, least of all a professional, would want to suggest otherwise.