It's a tactic to undermine your position without bothering to address the argument itself. Sometimes it comes up when the original post reeks of amateur hour or an individual has grown tired of debating self-proclaimed experts who read the Wikipedia page five minutes earlier. It's sometimes possible to get the debate back on track, but for the most part you're dealing with a debate tactic. You can have a meta-debate over whether such authority is necessary, but by that point you're far off course.
A logical debate can only take place when both sides agree and bind themselves by the appropriate rules. Unfortunately, many who debate online are not willing to engage on these terms.
Especially in the comments of political articles or about economic issues I find myself arguing with people who question my authority about a topic rather than refute my arguments.
----
Examples may be:
1:
Me: I think money printing by the Fed will cause inflation if they continue like this.
Random commenter: Are you an economist?
Me: I am not, but it's not relevant.
Random commenter: Ok, so you are clueless.
2:
Me: The current strategy to fight terror is not working because ISIS is growing.
Random commenter: What would you do to stop terrorism?
Me: I have an idea of what I would do, but it's not relevant because I'm not an expert, but do you think the current strategy is working?
Random commenter: So you don't know what you are talking about.
----
It is not about my opinions above, or even if I am right or not, I would gladly change my opinion after a debate, but I think that I am being disqualified unfairly.
If I am right, how should I answer or continue these conversations?