Edit (after I thought about it some more): I think ignorant would be best to use here, because stupid is also a slur that offends people for an inherent property, no real difference to retarded. I will edit my initial comment accordingly. Thank you for the heads up.

I just noticed your username and it made me feel so extremely disgusted that I am going to block you, just to never have to read it again, nothing personal though. Also, with such a username you are not in a particularly good position to criticize others for their choice of words imo.