I don't get easily offended but one thing really gets me going.
Movies that play it very loose with the truth. Hollywood is really one of the biggest culprits there as it is very US centric going so far to distort truth and facts so that the US or american people can be the heroes whereas facts and history have it play out totally different.
Case in point is the movie "U571" about a US submarine in WW2 that managed to obtain an Enigma code machine from the Germans when in reality it was a british crew who did this way before the US entered the war.
I get the reason why Hollywood does this but it still irks me.