Coughing has finally...
Coughing has finally overtaken speaking Arabic as the most taboo thing to do in an airport.
This is a "oneliner" joke that deals with the current Covid 19 pandemic. The joke states that it used to be considered to be the most taboo thing possible to speak Arabic in an airport, but now it reports that coughing is more taboo.
The reason why speaking Arabic is considered taboo is that the joke assumes that people in airports have anti-Arab feelings due to the possibility of Arab speaking people performing terrorist attacks against the airport. I am not going to discuss weather this is a valid fear, I am just saying that that is the reason why the joke assumes that speaking Arab is a taboo thing to do in an airport.
On the other hand, people that cough might have Covid 19, so if you were to cough in an airport people would be scared that you are going to pass on Covid to them.
The joke basically says that people are now more scared of catching covid than they are scared of terrorist attacks. Why is that funny? Probably because covid is generally not that dangerous compared to bombs and guns.
By the way - this is the current #1 one liner joke of all time on reddit, so a lot of people found this funny.