The "cause of all war" is not a settled issue academically. There are a variety of presentable theories attempting to describe the causes of some wars, and sevriis's answer is one of them. It's not demonstrably false - but it's also not demonstrably correct.
Your 'and probably' is where you totally lose me - I'm not sure when it started mattering if truth was offensive or not, and I'm not sure when you started caring if something was offensive or not, further I'm not sure when something being offensive began to register as something to be discouraged in your social projection, further further I'm not sure when or if you have or will ever hold yourself to any standard of acceptable offensiveness nor would you accept it if someone else held you to such a standard. All in all you're fucked in the head