You'd probably get the same question from a plumber if you asked him how to plug a pipe in a non-intuitive way. He has no way to know your pipes are laid out in a strange way, and the only spot you have left to add said junction without redoing your plumbing is back there - unless you tell him.
Sure, some people are assholes, but that's just people. Nobody's in your mind, they can't guess your requirements, thought process and level of experience. In my experience, more often than not, asking the question "why would you want to do that?" gets you a bad reason. "I did X this way because Y. I need Z." would filter the legitimate questioning out. From there, the others are just assholes, and those are everywhere.