The op didn't even mention mitmproxy is a terminal tool. You're being a little too sensitive by automatically assuming this is a GUI vs terminal war.

People would have less problem if the submitted was an open source tool, GUI or not.

P.S. Terminal application does have tremendous advantage when you work on a headless server. I used mitmproxy and it's great. The ncurse'd interface isn't harder to use than that of a GUI.