The bolt / fitting could be held in by the port plug, pull it out before going after it with a hammer, JUST IN CASE. The port maybe for a brake light switch activated by pressure.
I don't think that the banjo bolt is held in by the side port plug nor is it for a brake light switch. That's there for a brake line fitting with inverted flare in the port.That plug was installed by someone who replaced the brake line that was there with the tee just downstream of the line coming straight out of the master cylinder. This was discussed in
THIS THREAD started by jmoore. As far as getting the banjo bolt out of the fitting, the copper washer closest to the master cylinder has extruded into the threads of the bolt and is holding it in place.
