A relatively young Alec Guinness, probably best known as Obi-wan Kenobi in the Star Wars franchise, plays Prince Faisal in the 1962 film Lawrence of Arabia.
When he says "a little people, a silly people etc" Lawrence smiles because Faisal is quoting his own words back at him. He spoke them in an earlier encounter with Sherif Ali ibn el Kharish, played by Omar Sharif.
He is present in the above scene, sitting behind Lawrence. So this informs Lawrence these two talk to each other and Faisal knows all about the unpleasant encounter.
"Gun" in the military means artillery or similar. They mean "big guns," not firearms.
I'm a former military wife. My father was also career army though he retired when I was three.
Having been around military culture enough to know guns has a specific meaning in the military and it's not rifles, I cannot help but wonder if the British Colonel is being willfully obtuse and pretending "You ignorant Arabs who speak English as a second language can be easily blown off" while the Arabs are actually using the term correctly.