It’s not a question of “should” - an opinion piece is rhetoric, not reporting. You can fact check some of it sometimes but functionally can’t hold it to the same standards as a regular news article. I agree that this can sometimes lead to “alternative facts” and disingenuous arguments, but the only other option is to forbid the publication of them which is obviously an infringement of first amendment rights. It’s messy, and it can lead to people being misinformed, but it’s what we’re stuck with.