The "dumb" part is the attackers, and it's not an inability to speak, it's an inability to fucken think. Ignorancen times viciousnessn = these assholes.
"sign language is his only mode of communication", they say. Would they have said "Spanish is his only means of communication"? How about, "ASL is his only
We were chatting in the cafeteria once, about some dogs that were outside, and a dimbulb arose hisself up from the table between us and the window, swaggered over to our table and sez he knowed we wuz a-talkin' him, cuz he done seed us a-pointin right at him. Pointing is a pronoun in ASL, referring to the dog, in this case, but seeing as how the dog had more sense than him, we just told him to piss off. As if, we had nothing better than him to talk about.
So I knew you could catch shit for using that language, but stabbed? Fucking gang signs?