Actually, DonDiego added the "[Not Vegas Related]" to warn those who prefer not to read not-Vegas-related-posts. Apparently it did not act as a sufficient deterrent.
DonDiego posted the gif, because he found it amusing. That's all. And, as threads sometimes do, it stimulated some conversation about a current motion picture. DonDiego enjoys seeing a pleasant thread diverge topic-to-topic as different posters interpret things.
Nonetheless, DonDiego isn't bothered that LurkerPoster misjudged his motive. There's lots of folks on the internets who misread others' motives. DonDiego finds it difficult enough to just address whatever's been written; he doesn't try to read any motive into it.
In fact, DonDiego isn't bothered by much on the internets.
Some folks really, really like to post their political, even partisan political, views. If that's what they enjoy, far be it from DonDiego to deny them their pleasure. The owner of the website is the only fellow who's opinion should matter. DonDiego would communicate his dissatisfaction about the website to him, if he harbored any dissatisfaction, . . . which he doesn't.
On only two occasions has DonDiego communicated his objection to a post to the moderator. Both times were the same poster who: i. initiated the topic of assassination of then President G. W. Bush and ii. later initiated a thread addressing blowing people up in Las Vegas. (Maybe he had anger issues.) Anyway DonDiego communicated that he opined such posts might represent a danger to the reputation of the website. They were deleted.
Actually, as he typed "[Not Vegas Related]" in the original topic, he recalled when posts would regularly have a parenthetical tag attached, . . . like (POL) to designate it was, in fact, political. Maybe a return to those days would soothe those who object to particular topics. (DonDiego didn't really care for such parenthetical designations, because sometimes he just wanted to discuss "current events", . . . but readers would read political intentions where none were intended, . . . and sometimes turn the thread into a political one. But at least really intentional political posts could be identified by the initiator.)
Oh, and DonDiego won't be offended if LurkerPoster posts "potential, . . . (or actual), . . . useless shit". That's what the internets are for. It's not like there's somebody storing everything anybody types into a humongous data base in Utah, . . . or anything.