A portmanteau of "offended" and "humanitarian". It describes someone who has made a lifestyle out of finding deep offense in most any situation. Usually offense is found "on behalf" of other people who represent a definable group that the offenditarian themselves are clearly not a part of.
This is usually to make a display of "solidarity", an important word in the lexicon of offenditarians.
There is a strict hierarchy of human value, with handicapable African American lesbian female gendered womyn taking the top spot, and white cysgendered males being "worth" only 1/16th of the former.
The irony of offenditarianism is that if one becomes offended on behalf of someone higher on the value scale, the person higher up can use that to then become offended by the "patronizing," "colonialist" mindset of the offenditarian.
"Why is that girl running down the street and screaming at the ice cream truck?"
"The driver is wearing all white, a trademark outfit of early 20th Century eugenicists."
"Is the ice cream man a eugenicist?"
"No, but the girl is afraid someone might think he is, she is an offenditarian."