Perhaps you have been hearing of the word 'stupid' and you haven't dug deep into its meaning.
Basically, being stupid means you lack intelligence or maybe common sense.
Many people take this word 'stupid' which is always a normal abuse you throw to somebody to be a light word and these are the people who haven't considered following closely the deepest meaning of this word to understand what you actually are when somebody says you are so or when you call somebody stupid.
According to the Urban Dictionary, a stupid person is one characterized by mental dullness, foolishness, and lack of sense (senseless). You completely have no reason to live because you don't know life itself, you have no sense of life, you know and will never know anything about life.
When one refers to you as stupid it is the same as you standing in front of a clear and clean mirror alone but you still can't identify yourself in the mirror. You totally have no sense, you are insane and pointless, cooking without fire and you are busy waiting for your meals to get ready; this is what it means to be stupid.
When somebody calls you stupid especially after a disagreement then you should sit down and ask yourself what that person thinks of you but again you won't be able to see meaning in anything he or she said since you are stupid, senselessly inane and pompous if at all what he/she said is true.
Before calling somebody or something stupid, think of the meaning of the word stupid and relate if you should really refer to him/her/it as stupid. The pronunciation itself makes the word feel strange and annoying