'a case of opinion' is correct and usable in written English. It is usually used to refer to a subjective opinion, separate from facts or evidence, or when discussing different opinions a person or group may hold. For example, "The jury deliberated on the evidence, but ultimately the judge had to make a ruling based on his own case of opinion.".
"This is not a case of opinion or hyperbole," said Richard Emery, a lawyer for McNamee.
Is this just a case of one reasonable opinion versus another?
Rockstar responded in a statement, claiming "this is a case of people taking the opinions of a few anonymous posters on message boards as fact".
In the case of opinion articles, however, a misleading headline, like the one suggesting that genetically modified foods are dangerous, impaired a reader's ability to make accurate inferences.
"McIntyre had been wrongfully advised to pursue a case of discrimination based on political opinion because the anti-discrimination law in NSW does not make it unlawful to discriminate against a person on the basis of their political opinion," the commission heard.
It's not a case of trying to silence someone's opinion.
Saifuddin Bantasyam, a law lecturer who directs the Care Human-Rights Forum, an Aceh-based group, thinks the province could become a test case of international opinion.
Being a terminologist, I care about word choice. Ludwig simply helps me pick the best words for any translation. Five stars!
Maria Pia Montoro
Terminologist and Q/A Analyst @ Translation Centre for the Bodies of the European Union