Because op-eds are for controversial positions that are of public interest but aren't supported well enough or neutral enough for a news article. That's the definition. If it's clearly true you won't find it in an op-ed in general in any newspaper.
I'm sick of people who can't be bothered to look up terms they don't know using them to spuriously attack institutions that are crucial to our liberty in America.
If bias and inaccuracy was random then "it's just interesting blogs" might be an acceptable way for op-ed sections to go. When the problems trend obviously in one direction it becomes clear that the entire organisation has an agenda.
crucial to our liberty in America
As you may have guessed, I'm not American, and I'm sick of meeting Americans who have completely bizarre and distorted views of the UK because of the factually inaccurate nonsense they read in this supposedly high quality "newspaper".