If you get into a sign language argument with a deaf friend while they're brandishing swords then watch out! Your friend may have found themselves an interesting hobby, and after this argument they may want to tell you all about it!
Also why argue? Why not ask about the swords, that's interesting right? Swords man! Better than a stupid argument at least.
Also good for you for learning sign language so you can speak to your deaf friend.
Also, watch out! Sign language with swords is dangerous!