"Do your research before talking to me."

This sentiment should only ever apply to objective things that can be proven or established science. If someone tells me that the sun is a planet, well then maybe I would say do some research and then say get back to me. But more often than not, it's used to try and reinforce a subjective idea. "C*pitalism is better than X. Go do some research before you talk to me." And researching such a vast and complex topic (c*pitalism or otherwise) isn't something you can just Google quickly and become an expert on. "I'm right and you're wrong unless you go read the opinion article I read on yahoo" is not indicative of having researched a topic. You could research c*pitalism and have a more informed discussion about its nuances and its inner workings, but you're never going to have an objective answer as to why it is better than whatever else you're arguing against.

As a side note, I'm not trying to debate the merits of c*pitalism. Im just using it as an example to illustrate point.