It is very difficult to live in a world and argue something when that person expects you to be qualified in order to discuss the subject. This subject could be abortion, cancer, Policing tactics, psychology.
The person you’re arguing with normally makes an attempt to shut down any argument by asking you to put forth your diploma in the arts or sciences. Abortion isn’t safe? Huh? Are you a doctor, how would you know?
Yet another argument they present is that seeing as you didn’t have cancer, abortion or joined the police force and went through training that you’ve no authority to speak on it.
The “On what authority do you speak” goes all the way back to the Pharisees who posed the same question to Jesus. Humans haven’t changed and we still ask this of people going around talking about God and his healing power. “And what theological school did you go to? Are you a theologian? No? Then keep your mouth shut then.
Usually people resort to this when the discussion isn’t going their way or because they don’t possess the intellectual prowess required to discuss it to begin with and so this tactic is a lazy way out.
How do we respond to it? Well I often meet them on their own ground and ask them the same question. “Hey wait a minute you’ve been discussing the very same subject with me for the last five minutes and medicine isn’t your profession. Therefore if I’m not qualified neither are you. Regardless of this I’ll answer that question and tell you that an oncologist studies cancer but he doesn’t need to have contracted cancer in order to discuss and study this subject, likewise neither of us need a doctorate in science to study it and see that killing an unborn innocent human is wrong.