This is a meme community, so it's time to get serious!
This happened around 6 or 7 years ago. The company in question only has two work groups that are unionized -- Pilots and Dispatchers. Mechanics, Flight Attendants, Ground Service, etc. are not unionized.
Flight Attendants have attempted to unionize many times, but the vote always fails.
The poster included in this post was for Ramp workers -- the people who load baggage, marshal the planes into the gate, fill the potable water, etc. That vote ultimately failed, but these posters were only a small reason why. In my opinion, the biggest reason that other work groups don't want to unionize (they absolutely can, nothing is stopping them) is profit sharing.
Years ago the pilot union negotiated an extremely excellent profit sharing agreement, and it was negotiated for pilots only. Depending on the amount of profit for the year, employees can expect 10%-%20 of their yearly income paid in a lump sum. The company in question is typically very profitable (I can already see the "profit should be illegal" type of comments coming, but please spare me. I'm just trying to explain how it works).
Over time, other work groups started to catch wind of how much profit sharing pilots were getting. Naturally this sparked talk of unionizing in other work groups, so in order to calm things down the company extended the same profit sharing to all workers, not just the pilots.
This sort of reversed the desire to unionize for a lot of people (I disagree with them, but this is their thinking)... Now if the ramp personnel do unionize, they'd have to negotiate their own profit sharing as they would be excluded from the company wide payout. That's not to say they couldn't negotiate to keep the profit sharing, but the fear is real and people don't want to lose the big fat checks that come almost every year.
In summary, the workers aren't unionized but the company pays a lot of money to them to keep it that way. Would they be better off long term if they unionized? Yes, of course. But this poster, as ridiculous as it is, is not the only reason that work groups aren't voting in unions.
Here's a link to the AFA page talking about it a little bit https://deltaafa.org/news/profit-sharing-2025
There's also no accountability for companies and it has been like that for way too long. Look at Starbucks... some stores unionized so they just closed the stores and fired everyone. Completely illegal, but no consequences for the company. They succeeded in scaring the rest of the baristas, though, so mission accomplished.