How to debate when authority is questioned, but really not needed?

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.

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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.

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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?