Walking up to a stranger is one thing, but that really wasn't the case here... in this case, a comment was made to company-appointed P.R. representative who was present at a meeting with a journalist who was there to write about the company, its values, and its culture. I think the founder of the company commenting on the same company's P.R. person not adhering to the company's values is very much him "minding his own business".
True in some cases, but would you seriously put a single-use bottle into that category? The harm from that, while undeniably real, doesn't seem immediate or severe enough to justify jumping past civility to disrespect. You made a statement that disrespect is generally acceptable, and I disagree. While there are exceptions, disrespect should generally be avoided. To make the point even more bluntly, I think normalizing disrespect makes assholes of us all.
You’re jumping backwards and forwards between the specific and the general here, but yes, I think it’s appropriate to admonish a PR person who knows there’s a journalist around for being off brand because _that’s literally their job_.
To speak to “it makes assholes of all of us”, appeals to civility and politeness have a long and sordid history of being used to oppress people, cf tone policing.
So does rejection of civility and politeness. Those who would marginalize or oppress others always start by placing them outside the sphere of social conventions, then complain about "political correctness" and "tone policing" when they're called on their behavior toward anyone not of their own tribe.
I suspect the set of people who've complained about both political correctness _and_ tone policing is precisely zero.
When people started having personal choices that affected the people around them. So: since always.