People who uses the word "obnoxious" are also obnoxious. There are many unpleasant words, you have to use some of them and people don't like any of them.
Would you refer to someone as a midwit in a typical office environment and expect your professional reputation to remain intact? If you were to do this on an ongoing basis for whatever reason, how long before you're asked to have a little chat with the folks in HR? Would you then attempt to explain it away as one of those unpleasant words that you just had to use? I want to be there for that conversation.
The word “obnoxious” does not carry the connotation of smug superiority that “midwit” does.