They get irritated because, if you didn't know, it's probably ten times more stressful to them than it is to you and some people DO NOT know how to handle stress.
It's the first time that it has happened to you with him. I guarantee it was not the first time that they are not understood. Chill out, be patient and yuo will see their attitude change %100 no matter it it's spanish, chinese, korean....you name it.


/rant